Cleavage Products (cleavage + products)

Distribution by Scientific Domains


Selected Abstracts


Tebuconazole dissipation and metabolism in Tifton loamy sand during laboratory incubation,

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2004
Timothy C Strickland
Abstract The fungicide tebuconazole is widely used to control soil-borne and foliar diseases in peanuts and other crops. No published data are currently available on the extent and rate at which this compound degrades in soil. Unpublished data summarized in registration documents suggest that the compound is persistent, with 300,600 days half-life. We conducted a 63-day laboratory incubation to evaluate tebuconazole's dissipation kinetics and impact on soil microbial activity in Tifton loamy sand. Tifton soils support extensive peanut production in the Atlantic Coastal Plain region of Georgia and Alabama. Products containing tebuconazole are applied to an estimated 50% of the peanut acreage in the region. At the end of the incubation, 43 (±42)% of the parent compound was recovered in soil extracts. The first-order kinetic model, which gave a good fit to the dissipation data (r2 = 0.857), yielded a soil half-life (t1/2) of 49 days. This is 6,12 times more rapid than t1/2 values described in unpublished tebuconazole registration documents. Four degradates were identified. Tentative structural assignments indicated that degradates were derived from hydroxylation of the parent compound and/or chlorophenyl ring cleavage. Cleavage products showed a steady increase during the incubation, and on a molar basis were equal to 63% of the time zero tebuconazole concentration. No significant effect on soil microbial biomass was observed, indicating that when the compound is applied at normal agronomic rate it does not impact soil metabolic activity. Use of the soil-half life data derived in this study should improve the accuracy of tebuconazole fate assessments for Coastal Plain peanut production. The study also indicated that environmental assessment of selected degradates may be needed to fully evaluate risks of tebuconazole use. Published in 2004 for SCI by John Wiley & Sons, Ltd. [source]


1-D-Tin(II) Phenylchalcogenolato Complexes ,1[Sn(EPh)2] (E = S, Se, Te) , Synthesis, Structures, Quantum Chemical Studies and Thermal Behaviour

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2010
Andreas Eichhöfer
Abstract A series of three 1-D-tin(II) phenylchalcogenolato complexes ,1[Sn(EPh)2] (E = S, Se, Te) were synthesized in yields > 80,% by reaction of SnCl2 with two equivalents of PhESiMe3 in organic solvents. In the crystal the molecules form two different types of one-dimensional chains. In ,1[Sn(SPh)2] the tin atoms are distorted trigonal pyramidal coordinated by sulfur atoms (two bonds within a monomer and one longer bond between neighbored monomers), while in ,1[Sn(EPh)2] (E = Se, Te) the tin atoms show contacts to two neighbored monomers leading to a fourfold coordination of the tin atoms by either selenium or tellurium atoms. The bond situation is discussed on the basis of density functional calculations. Thermal treatment mostly leads to the formation of the corresponding phase pure tin(II) chalcogenides however sublimation plays an increasing role ongoing from the tellurolato to the thiolato complex especially for the use of vacuum conditions. The investigation of the volatile cleavage products reveals the occurence of more complex reactions in the gas phase than the formal stoichiometric cleavage of EPh2 (E = S, Se, Te) with formation of SnE. [source]


How do enamelysin and kallikrein 4 process the 32-kDa enamelin?

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006
Yasuo Yamakoshi
The activities of two proteases , enamelysin (MMP-20) and kallikrein 4 (KLK4) , are necessary for dental enamel to achieve its high degree of mineralization. We hypothesize that the selected enamel protein cleavage products which accumulate in the secretory-stage enamel matrix do so because they are resistant to further cleavage by MMP-20. Later, they are degraded by KLK4. The 32-kDa enamelin is the only domain of the parent protein that accumulates in the deeper enamel. Our objective was to identify the cleavage sites of 32-kDa enamelin that are generated by proteolysis with MMP-20 and KLK4. Enamelysin, KLK4, the major amelogenin isoform (P173), and the 32-kDa enamelin were isolated from developing porcine enamel. P173 and the 32-kDa enamelin were incubated with MMP-20 or KLK4 for up to 48 h. Then, the 32-kDa enamelin digestion products were fractionated by reverse-phase high-performance liquid chromatography (RP-HPLC) and characterized by Edman sequencing, amino acid analysis, and mass spectrometry. Enamelysin cleaved the 32-kDa enamelin only after it was deglycosylated. Kallikrein 4 digestion of the 32-kDa enamelin generated nine major cleavage products, six of which were successfully characterized. After 12 h of digestion with KLK4, all of the 32-kDa enamelin had been cleaved, but some cleavage products persisted after 48 h of digestion. [source]


A novel 2D-based approach to the discovery of candidate substrates for the metalloendopeptidase meprin

FEBS JOURNAL, Issue 18 2008
Daniel Ambort
In the past, protease-substrate finding proved to be rather haphazard and was executed by in vitro cleavage assays using singly selected targets. In the present study, we report the first protease proteomic approach applied to meprin, an astacin-like metalloendopeptidase, to determine physiological substrates in a cell-based system of Madin,Darby canine kidney epithelial cells. A simple 2D IEF/SDS/PAGE-based image analysis procedure was designed to find candidate substrates in conditioned media of Madin,Darby canine kidney cells expressing meprin in zymogen or in active form. The method enabled the discovery of hitherto unkown meprin substrates with shortened (non-trypsin-generated) N- and C-terminally truncated cleavage products in peptide fragments upon LC-MS/MS analysis. Of 22 (17 nonredundant) candidate substrates identified, the proteolytic processing of vinculin, lysyl oxidase, collagen type V and annexin A1 was analysed by means of immunoblotting validation experiments. The classification of substrates into functional groups may propose new functions for meprins in the regulation of cell homeostasis and the extracellular environment, and in innate immunity, respectively. [source]


RNase P RNA-mediated cleavage

IUBMB LIFE, Issue 3 2009
Leif A. Kirsebom
Abstract Metal(II)-induced hydrolysis of RNA produce products with 5,-hydroxyls and 2,;3,-cyclic phosphates at the ends. Ribozymes are RNA molecules that act as catalysts. Some ribozymes that cleave RNA also generate 5,-hydroxyls and 2,;3,-cyclic phosphates whereas others produces 5,-phosphates and 3,-hydroxyls at the ends of the cleavage products. RNase P is an essential endoribonuclease involved in RNA processing. The catalytic RNA subunit of RNase P is a trans-acting ribozyme that cleaves various RNA substrates in vitro generating 5,-phosphates and 3,-hydroxyls as cleavage products. The activity depends on the presence of metal(II) ions such as Mg2+. RNase P RNA has therefore to facilitate a nucleophilic attack that generates the correct product ends and prevent metal(II)-induced hydrolysis of the RNA substrate. In this review, we will discuss our current understanding of the interactions between RNase P RNA and its substrate, role of specific residues with respect to catalysis and positioning of functionally important Mg2+ at and in the vicinity of the cleavage site that ensures that products with correct ends are generated. Moreover, we will discuss the composition of RNase P and its RNA subunit in an evolutionary perspective. © 2009 IUBMB IUBMB Life, 61(3):189,200, 2009 [source]


Two laccase isoforms of the basidiomycete Cerrena unicolor VKMF-3196.

JOURNAL OF BASIC MICROBIOLOGY, Issue 1 2010
Induction, isolation, properties
Abstract The laccase induction in submerged culture of basidiomycete Cerrena unicolor VKM F-3196 was investigated. Cu2+ at concentration 0.1 mM was an optimum inducer of C. unicolor laccase. Two isoforms of laccase, namely LacC1 and LacC2, were isolated and characterized. The isoforms were shown to have different physical-chemical and catalytic properties. On the basis of the MALDI TOF MS analysis of tryptic cleavage products of both the proteins and N-terminal amino-acid sequences analysis two isoforms of laccase (LacC1 and LacC2) were classified as products of two different genes. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Discovery, regulation, and action of the major apoptotic nucleases DFF40/CAD and endonuclease G

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2005
Piotr Widlak
Abstract Toward the end of the 20th and beginning of the 21st centuries, clever in vitro biochemical complementation experiments and genetic screens from the laboratories of Xiaodong Wang, Shigekazu Nagata, and Ding Xue led to the discovery of two major apoptotic nucleases, termed DNA fragmentation factor (DFF) or caspase-activated DNase (CAD) and endonuclease G (Endo G). Both endonucleases attack chromatin to yield 3,-hydroxyl groups and 5,-phosphate residues, first at the level of 50,300 kb cleavage products and next at the level of internucleosomal DNA fragmentation, but these nucleases possess completely different cellular locations in normal cells and are regulated in vastly different ways. In non-apoptotic cells, DFF exists in the nucleus as a heterodimer, composed of a 45 kD chaperone and inhibitor subunit (DFF45) [also called inhibitor of CAD (ICAD-L)] and a 40 kD latent nuclease subunit (DFF40/CAD). Apoptotic activation of caspase-3 or -7 results in the cleavage of DFF45/ICAD and release of active DFF40/CAD nuclease. DFF40's nuclease activity is further activated by specific chromosomal proteins, such as histone H1, HMGB1/2, and topoisomerase II. DFF is regulated by multiple pre- and post-activation fail-safe steps, which include the requirements for DFF45/ICAD, Hsp70, and Hsp40 proteins to mediate appropriate folding during translation to generate a potentially activatable nuclease, and the synthesis in stoichiometric excess of the inhibitors (DFF45/35; ICAD-S/L). By contrast, Endo G resides in the mitochondrial intermembrane space in normal cells, and is released into the nucleus upon apoptotic disruption of mitochondrial membrane permeability in association with co-activators such as apoptosis-inducing factor (AIF). Understanding further regulatory check-points involved in safeguarding non-apoptotic cells against accidental activation of these nucleases remain as future challenges, as well as designing ways to selectively activate these nucleases in tumor cells. © 2005 Wiley-Liss, Inc. [source]


Assessment of naphthalene biodegradation efficiency of Pseudomonas and Burkholderia strains tested in soil model systems,

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2006
Andrei E Filonov
Abstract The kinetic parameters of the naphthalene degradation process performed by indigenous and introduced microorganisms were studied in soil model systems. The introduction of active naphthalene-degrading strains Pseudomonas putida BS3701 and G7 in soil model systems accelerated the naphthalene destruction process by a factor of three to four. Moreover, the addition of salicylate (0.1 mg g,1 dry soil) to the systems containing the introduced microbial strains again doubled the rate of the naphthalene degradation process. To provide a quantitative assessment of the naphthalene biodegradation process, a mathematical model describing the bacterial growth, the consumption of the naphthalene, the production and subsequent consumption of naphthalene cleavage products, and the consumption of organic soil substances in soil model systems was developed. An approach for assessment of the degradation efficiency of low solubility polycyclic aromatic hydrocarbon provided by bacteria of genera Pseudomonas and Burkholderia in soil was suggested. The approach will enable comparison and selection of the most active degraders, which have the potential for application in biotechnologies for cleaning of soils contaminated by polycyclic aromatic hydrocarbons. Copyright © 2005 Society of Chemical Industry [source]


A personal account of the role of peptide research in drug discovery: the case of hepatitis C,

JOURNAL OF PEPTIDE SCIENCE, Issue 1 2001
Antonello Pessi
Abstract Although peptides themselves are not usually the end products of a drug discovery effort, peptide research often plays a key role in many aspects of this process. This will be illustrated by reviewing the experience of peptide research carried out at IRBM in the course of our study of hepatitis C virus (HCV). The target of our work is the NS3/4A protease, which is essential for maturation of the viral polyprotein. After a thorough examination of its substrate specificity we fine-tuned several substrate-derived peptides for enzymology studies, high-throughput screening and as fluorescent probes for secondary binding assays. In the course of these studies we made the key observation: that the protease is inhibited by its own cleavage products. Single analog and combinatorial optimization then derived potent peptide inhibitors. The crucial role of the NS4A cofactor was also addressed. NS4A is a small transmembrane protein, whose central domain is the minimal region sufficient for enzyme activation. Structural studies were performed with a peptide corresponding to the minimal activation domain, with a series of product inhibitors and with both. We found that NS3/4A is an induced fit enzyme, requiring both the cofactor and the substrate to acquire its bioactive conformation; this explained some puzzling results of ,serine-trap' type inhibitors. A more complete study on NS3 activation, however, requires the availability of the full-length NS4A protein. This was prepared by native chemical ligation, after sequence engineering to enhance its solubility; structural studies are in progress. Current work is focused on the P, region of the substrate, which, at variance with the P region, is not used for ground state binding to the enzyme and might give rise to inhibitors showing novel interactions with the enzyme. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd. [source]


Effects of porcine 25 kDa amelogenin and its proteolytic derivatives on bone sialoprotein expression

JOURNAL OF PERIODONTAL RESEARCH, Issue 5 2010
Y. Nakayama
Nakayama Y, Yang L, Mezawa M, Araki S, Li Z, Wang Z, Sasaki Y, Takai H, Nakao S, Fukae M, Ogata Y. Effects of porcine 25 kDa amelogenin and its proteolytic derivatives on bone sialoprotein expression. J Periodont Res 2010; 45: 602,611. © 2010 John Wiley & Sons A/S Background and Objective:, Amelogenins are hydrophobic proteins that are the major component of developing enamel. Enamel matrix derivative has been used for periodontal regeneration. Bone sialoprotein is an early phenotypic marker of osteoblast differentiation. In this study, we examined the ability of porcine amelogenins to regulate bone sialoprotein transcription. Material and Methods:, To determine the molecular basis of the transcriptional regulation of the bone sialoprotein gene by amelogenins, we conducted northern hybridization, transient transfection analyses and gel mobility shift assays using the osteoblast-like ROS 17/2.8 cells. Results:, Amelogenins (100 ng/mL) up-regulated bone sialoprotein mRNA at 3 h, with maximal mRNA expression occurring at 12 h (25 and 20 kDa) and 6 h (13 and 6 kDa). Amelogenins (100 ng/mL, 12 h) increased luciferase activities in pLUC3 (nucleotides ,116 to +60), and 6 kDa amelogenin up-regulated pLUC4 (nucleotides ,425 to +60) activity. The tyrosine kinase inhibitor inhibited amelogenin-induced luciferase activities, whereas the protein kinase A inhibitor abolished 25 kDa amelogenin-induced bone sialoprotein transcription. The effects of amelogenins were abrogated by 2-bp mutations in the fibroblast growth factor 2 response element (FRE). Gel-shift assays with radiolabeled FRE, homeodomain-protein binding site (HOX) and transforming growth factor-beta1 activation element (TAE) double-strand oligonucleotides revealed increased binding of nuclear proteins from amelogenin-stimulated ROS 17/2.8 cells at 3 h (25 and 13 kDa) and 6 h (20 and 6 kDa). Conclusion:, These results demonstrate that porcine 25 kDa amelogenin and its proteolytic derivatives stimulate bone sialoprotein transcription by targeting FRE, HOX and TAE in the bone sialoprotein gene promoter, and that full-length amelogenin and amelogenin cleavage products are able to regulate bone sialoprotein transcription via different signaling pathways. [source]


A domain level interaction network of amyloid precursor protein and A, of Alzheimer's disease

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 12 2010
Victoria M. Perreau
Abstract The primary constituent of the amyloid plaque, ,-amyloid (A,), is thought to be the causal "toxic moiety" of Alzheimer's disease. However, despite much work focused on both A, and its parent protein, amyloid precursor protein (APP), the functional roles of APP and its cleavage products remain to be fully elucidated. Protein,protein interaction networks can provide insight into protein function, however, high-throughput data often report false positives and are in frequent disagreement with low-throughput experiments. Moreover, the complexity of the CNS is likely to be under represented in such databases. Therefore, we curated the published work characterizing both APP and A, to create a protein interaction network of APP and its proteolytic cleavage products, with annotation, where possible, to the level of APP binding domain and isoform. This is the first time that an interactome has been refined to domain level, essential for the interpretation of APP due to the presence of multiple isoforms and processed fragments. Gene ontology and network analysis were used to identify potentially novel functional relationships among interacting proteins. [source]


Proteomic analysis identifies in vivo candidate matrix metalloproteinase-9 substrates in the left ventricle post-myocardial infarction

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 11 2010
Rogelio Zamilpa
Abstract Matrix metalloproteinase-9 (MMP-9) deletion has been shown to improve remodeling of the left ventricle post-myocardial infarction (MI), but the mechanisms to explain this improvement have not been fully elucidated. MMP-9 has a broad range of in vitro substrates, but relevant in vivo substrates are incompletely defined. Accordingly, we evaluated the infarct regions of wild-type (wt) and MMP-9 null (null) mice using a proteomic strategy. Wt and null groups showed similar infarct sizes (48±3 in wt and 45±3% in null), indicating that both groups received an equal injury stimulus. Left ventricle infarct tissue was homogenized and analyzed by 2-DE and MS. Of 31 spot intensity differences, the intensities of 9 spots were higher and 22 spots were lower in null mice compared to wt (all p<0.05). Several extracellular matrix proteins were identified in these spots by MS, including fibronectin, tenascin-C, thrombospondin-1, and laminin. Fibronectin was observed on the gels at a lower than expected molecular weight in the wt group, which suggested substrate cleavage, and the lower molecular weight spot was observed at lower intensity in the MMP-9 null group, which suggested cleavage by MMP-9. Immunoblotting confirmed the presence of fibronectin cleavage products in the wt samples and lower levels in the absence of MMP-9. In conclusion, examining infarct tissue from wt and MMP-9 null mice by proteomic analysis provides a powerful and unique method to identify in vivo candidate MMP substrates. [source]


Electrospray ionization ion trap mass spectrometry for structural characterization of oligosaccharides derivatized with 2-aminobenzamide

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2005
Willy Morelle
The use of electrospray ionization (ESI) quadrupole ion trap mass spectrometry and reversed-phase high-performance liquid chromatography (HPLC) for the characterization of 2-aminobenzamide (2AB)-labeled oligosaccharides and N-linked protein oligosaccharide mixtures is described. The major signals were obtained under these conditions from the [M+Na]+ ions for all 2AB-derivatized oligosaccharides. Under collision-induced dissociation, sodiated molecular species generated in the ESI mode yield simple and predictable mass spectra. Tandem mass spectrometry (MS/MS) experiments with orders higher than two offer a number of ways to enhance MS/MS spectra and to derive information not present in MS and MS2 spectra. Information on composition, sequence, branching and, to some extent, interglycosidic linkages can be deduced from fragments resulting from the cleavage of glycosidic bonds and from weak cross-ring cleavage products. Reversed-phase HPLC and derivatization by reductive amination using 2-aminobenzamide were finally applied to characterize a glycan pool enzymatically released from glycoproteins. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Cathepsin protease activity modulates amyloid load in extracerebral amyloidosis

THE JOURNAL OF PATHOLOGY, Issue 4 2006
C Röcken
Abstract In cerebral amyloidoses, such as Alzheimer's disease, proteolytic processing of the precursor protein is a fundamental mechanism of the disease, since it generates the amyloid protein. However, the putative significance of proteases in extracerebral amyloidoses is less well defined. In this study, we investigated the biological significance of cathepsin (Cath) B, CathK, and CathL in the pathology and pathogenesis of extracerebral amyloidoses by using the murine model of reactive or secondary AA amyloidosis with three different cathepsin-deficient mouse strains. Extracerebral AA amyloid was induced by injecting amyloid-enhancing factor and silver nitrate into CathB,/,, CathK,/,, and CathL,/, mice. Wild-type mice served as a control. CathK,/, mice deposited over 90% more amyloid and CathL,/, mice 60% less amyloid than the control (p < 0.0001). The amyloid load in CathB,/, mice did not differ from that in wild-type mice. In vitro degradation experiments with recombinant human and murine serum amyloid A (SAA) 1.1 and CathK and CathL showed that CathL generates a large number of differently sized SAA cleavage products. One of these fragments spans the heparin/heparan sulphate binding site and the neutral cholesterol ester hydrolase activating region of SAA. CathK showed only endoproteolytic activity and did not generate any AA amyloid-like peptides. This study provides unequivocal evidence that proteases modulate amyloid load in extracerebral amyloidosis. CathL was identified as an amyloid-promoting and CathK as an amyloid-retarding cysteine protease. CathB may only modulate the primary structure of the amyloid peptide without affecting amyloid load. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source]


The combination of the antitumoural pyridyl cyanoguanidine CHS 828 and etoposide in vitro,from cytotoxic synergy to complete inhibition of apoptosis

BRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2002
P Martinsson
The present study was aimed at elucidating the apoptosis inhibitory properties of the cyanoguanidine CHS 828. CHS 828 exhibits impressive cytotoxic activity in vitro and in vivo. Apoptosis is not its main mode of cytotoxic effect, and we have previously proposed a dual mechanism, where CHS 828 inhibits its own cell death pathways. Etoposide on the other hand, is a well-established anticancer agent with documented effect in a number of malignancies, induces apoptosis through extensively studied caspase dependent pathways. Here we studied the combined effect of the two drugs in the human lymphoma cell line U-937 GTB. Cytotoxicity was evaluated as total viability measured by the fluorometric microculture cytotoxicity assay (FMCA). Caspase activity was assessed by colorimetric detection of specific cleavage products for caspases 3, 8 and 9, respectively. Morphology was evaluated in May-Grünwald/Giemsa stained preparations. Interaction analysis based on FMCA results of simple combination exposure revealed impressive synergistic effect on cell kill. Detailed investigations of the kinetics involved showed that short pre-exposure (0,12 h) to CHS 828 enhanced caspase activation by etoposide, while longer pre-exposure (18,48 h) inhibited both caspase activation and apoptotic morphology otherwise induced by etoposide. The present results support the theory that CHS 828 block specific cell death pathways. The synergistic results are promising for future combination trials in animals, however, different dosing schedules should be considered, in order to investigate whether the above findings translate into the in vivo setting. British Journal of Pharmacology (2002) 137, 568,573. doi:10.1038/sj.bjp.0704888 [source]


A Novel Tripodal Ligand Containing Three Different N -Heterocyclic Donor Functions and Its Application in Catechol Dioxygenase Mimicking

CHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2009
Marit Wagner Dipl.-Chem.
Abstract Prominent donors: A pyridyl, an imidazolyl, and a pyrazolyl donor function are part of the novel tripodal ligand depicted, which thus combines three of the most prominent donors applied in ligands for bioinorganic chemistry within one coordination unit. To exploit its behaviour and potential, first investigations have been carried out in relation to catechol dioxygenase mimicry. We describe a novel chiral ligand, L, in which three different N -donor functions are linked to a methoxymethine unit: a methylpyrazole derivative, a methylimidazole unit, and a pyridyl residue. Complexes with FeCl2, FeBr2, and FeCl3 have been synthesized and fully characterized, including with respect to their molecular structures. While in combination with FeCl3L coordinates in a tripodal fashion, with FeX2 (X=Cl, Br) it binds only through two functions and the pyridyl unit remains dangling. For potential modelling of intradiol and extradiol catechol dioxygenase reactivity, the complexes [LFeCl2], 1, and [LFeCl3], 3, have been treated with 3,5-di- tert -butylcatechol, triethylamine, and O2. Both complexes yielded similar results in such investigations, since the LFeII,catecholate complex reacts with O2 through one-electron oxidation in the first step. Employing 3 in acetonitrile solution, intradiol cleavage occurred, although the undesired quinone was formed as the main product. If reagents were added (NaBPh4, H+) or reaction conditions were chosen (CH2Cl2 instead of CH3CN as the solvent) that made the coordination sphere at the iron centre more accessible for a third substrate donor function, an alternative reaction route, presumably involving O2 binding at the metal, became more important, which led to extradiol cleavage. In the extreme case (CH2Cl2 as the solvent and with the addition of NaBPh4), mainly the extradiol cleavage products were formed; the intradiol products were only observed as side products then and quinone formation became negligible. Protonated base functions in the second coordination sphere increased the efficiency of extradiol cleavage only slightly. The obtained results are in line with current understanding of the function of intradiol/extradiol dioxygenases. [source]