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Enantiopure Compounds (enantiopure + compound)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Mutations towards enantioselectivity adversely affect secretion of Pseudomonas aeruginosa lipase

FEMS MICROBIOLOGY LETTERS, Issue 1 2008
Sascha Hausmann
Abstract Lipases are important biocatalysts used as detergent additives to manufacture biodiesel, and in particular, for the production of enantiopure compounds such as alcohols, amines and carboxylic acids. Extensive efforts were conducted trying to optimize lipase properties and lipase LipA of Pseudomonas aeruginosa comprises the best-studied example in terms of optimizing enantioselectivity by application of numerous directed evolution methods. Its enantioselectivity in the asymmetric hydrolysis of the model substrate 2-methyldecanoic acid p -nitrophenyl ester was increased from E=1.1 for the wild-type enzyme to E=51 for the best (S)-enantioselective variant which carried six amino acid exchanges. We have observed that overexpression of this variant in the homologous host resulted in only marginal yields of enzyme in the bacterial culture supernatant, suggesting that the enantioselective LipA variant was secreted with only low efficiency. Hence, we have analysed the secretion of this lipase variant and compared it to variants carrying either the respective single mutations or some combinations. We report here the identification of two amino acid substitutions located on the protein surface, which significantly impair lipase secretion. [source]

Nature versus nurture in two highly enantioselective esterases from Bacillus cereus and Thermoanaerobacter tengcongensis

MICROBIAL BIOTECHNOLOGY, Issue 1 2010
Stephan Grosse
Summary There is an increasing need for the use of biocatalysis to obtain enantiopure compounds as chiral building blocks for drug synthesis such as antibiotics. The principal findings of this study are: (i) the complete sequenced genomes of Bacillus cereus ATCC 14579 and Thermoanaerobacter tengcongensis MB4 contain a hitherto undescribed enantioselective and alkaliphilic esterase (BcEST and TtEST respectively) that is specific for the production of (R)-2-benzyloxy-propionic acid ethyl ester, a key intermediate in the synthesis of levofloxacin, a potent antibiotic; and (ii) directed evolution targeted for increased thermostability of BcEST produced two improved variants, but in either case the 3,5°C increase in the apparent melting temperature (Tm) of the mutants over the native BcEST that has a Tm of 50°C was outperformed by TtEST, a naturally occurring homologue with a Tm of 65°C. Protein modelling of BcEST mapped the S148C and K272R mutations at protein surface and the I88T and Q110L mutations at more buried locations. This work expands the repertoire of characterized members of the ,/,-fold hydrolase superfamily. Further, it shows that genome mining is an economical option for new biocatalyst discovery and we provide a rare example of a naturally occurring thermostable biocatalyst that outperforms experimentally evolved homologues that carry out the same hydrolysis. [source]

Cover Picture: Biotechnology Journal 5/2006

BIOTECHNOLOGY JOURNAL, Issue 5 2006
Article first published online: 11 MAY 200
Cover illustration: Chirality is omnipresent in nature: Many compounds contain an asymmetric center and thus can occur in two non-superimposable mirror-image forms (enantiomers). The two enantiomers of a chiral compound often have dramatically different effects, as exemplified by the thalidomid catastrophe. Therefore, only one enantiomer is needed for the production of active substances in the pharmaceutical or agricultural industry. It is an important aspect in white biotechnology, to take advantage of highly specific catalysts of (micro-) biological origin for the synthesis of enantiopure compounds. Biocatalysis indeed is a highly efficient process and an example of environmentally friendly, ,green' chemistry, requiring relatively low energy inputs, mild solvents and generating minimal byproducts. Image © Wacker. [source]

Determination of absolute configurations by X-ray crystallography and 1H NMR anisotropy

CHIRALITY, Issue 5 2008
Nobuyuki Harada
Abstract To determine the absolute configurations of chiral compounds, many spectroscopic and diffraction methods have been developed. Among them, X-ray crystallographic Bijvoet method, CD exciton chirality method, and the combination of vibrational circular dichroism and quantum mechanical calculations are of nonempirical nature. On the other hand, X-ray crystallography using a chiral internal reference, and 1H NMR spectroscopy using chiral anisotropy reagents are relative and/or empirical methods. In addition to absolute configurational determinations, preparations of enantiopure compounds are strongly desired. As chiral reagents useful for both the preparation of enantiopure compounds by HPLC separation and the simultaneous determination of their absolute configurations, we have developed camphorsultam dichlorophthalic acid (CSDP acid) for X-ray crystallography and 2-methoxy-2-(1-naphthyl)propionic acid (M,NP acid) for 1H NMR spectroscopy. In this review, the principles and applications of these X-ray and NMR methods are explained using mostly our own data. Chirality, 2008. © 2007 Wiley-Liss, Inc. [source]