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Sulfur-containing Amino Acids (sulfur-containing + amino_acids)
Selected AbstractsMethionine gamma-lyase: The unique reaction mechanism, physiological roles, and therapeutic applications against infectious diseases and cancersIUBMB LIFE, Issue 11 2009Dan Sato Abstract Sulfur-containing amino acids (SAAs) are essential components in many biological processes and ubiquitously distributed to all organisms. Both biosynthetic and catabolic pathways of SAAs are heterogeneous among organisms and between developmental stages, and regulated by the environmental changes. Limited lineage of organisms ranging from archaea to plants, but not human, possess a unique enzyme methionine gamma-lyase (MGL, EC 4.4.1.11) to directly degrade SAA to ,-keto acids, ammonia, and volatile thiols. The reaction mechanisms and the physiological roles of this enzyme are partially demonstrated by the enzymological analyzes, structure determination, isotopic labeling of the intermediate metabolites, and functional analyzes of deficient mutants. MGL has been exploited as a drug target for the infectious diseases caused by parasitic protozoa and anaerobic periodontal bacteria. In addition, MGL has been utilized to develop therapeutic interventions of various cancers, by introducing recombinant proteins to deplete methionine essential for the growth of cancer cells. In this review, we discuss the current understanding of enzymological properties, putative physiological roles, and therapeutic applications of MGL. © 2009 IUBMB IUBMB Life, 61(11): 1019,1028, 2009 [source] Antioxidative activity of sulfur-containing compounds in Allium species for human LDL oxidation in vitroBIOFACTORS, Issue 1-4 2004Hiroyuki Nishimura Abstract Sulfur-containing compounds contributing to health promotion in Allium species are produced via enzymic and thermochemical reactions. Sulfur-containing amino acids and volatile organosulfur compounds were prepared for an antioxidative assay. The inhibitory activity of S-alk(en)yl-L-cysteines and their sulfoxides, volatile alk(en)yl disulfides and trisulfides, and vinyldithiins in Allium species against lipid hydroperoxide (LOOH) formation in human low-density lipoprotein (LDL) was examined. It was elucidated that the alk(en)yl substituents (methyl, propyl, and allyl) and the number of sulfur atoms in the compounds were important for the antioxidative activity. 3,4-Dihydro-3-vinyl-1,2-dithiin, which is produced by a thermochemical reaction of allyl 2-propenethiosulfinate, exhibited the highest antioxidative activity of human LDL among sulfur-containing compounds. [source] Distribution of carbon-14 labeled C60 ([14C]C60) in the pregnant and in the lactating dam and the effect of C60 exposure on the biochemical profile of urineJOURNAL OF APPLIED TOXICOLOGY, Issue 4 2010Susan C. J. Sumner Abstract This study was conducted to determine the distribution of [14C]C60 in the pregnant rat and fetuses, and in the lactating rat and offspring. Pregnant rats were dosed on gestation day (gd) 15 and lactating rats were dosed on postnatal day (pnd) 8 via tail vein injection with a suspension of ,0.3,mg [14C]C60,kg,1 body weight prepared in polyvinylpyrrolidone (PVP), or with PVP alone. Tissues were collected at 24 and 48 h after dosing. The largest portion of the administered dose was detected in the liver (,43%, pregnant dam; ,35%, lactating dam) and lung (,25%, lactating dam). Radioactivity (,6%) was distributed to the reproductive tract, placenta and fetuses of the pregnant dam. Lactating rats had radioactivity distributed to the milk (3140,dpm,g,1 tissue, 24,h; 1620,dpm,g,1 tissue, 48,h), and to the pups' GI tract (2.8%, 24,h; 4.4% 48,h) and liver (<1%). Blood radioactivity was significant at 24,h (14,19%) and at 48,h (7%) after dosing; largely accounted for in the plasma fraction. Less that 4% of the dose was recovered in the maternal spleen, heart, brain, urine or feces. Metabolomics analysis of urine indicated that dams exposed to [14C]C60 had decreased metabolites derived from the Krebs cycle and increased metabolites derived from the urea cycle or glycolysis, as well as alterations in the levels of some sulfur-containing amino acids and purine/pyrimidine metabolites. This study demonstrated that [14C]C60 crosses the placenta and is transmitted to offspring via the dam's milk and subsequently systemically absorbed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Studies on deprotection of cysteine and selenocysteine side-chain protecting groupsJOURNAL OF PEPTIDE SCIENCE, Issue 2 2007Katharine M. Harris Abstract We present here a simple method for deprotecting p -methoxybenzyl groups and acetamidomethyl groups from the side-chains of cysteine and selenocysteine. This method uses the highly elecrophilic, aromatic disulfides 2,2,-dithiobis(5-nitropyridine) (DTNP) and 2,2,-dithiodipyridine (DTP) dissolved in TFA to effect removal of these heretofore difficult-to-remove protecting groups. The dissolution of these reagents in TFA, in fact, serves to ,activate' them for the deprotection reaction because protonation of the nitrogen atom of the pyridine ring makes the disulfide bond more electrophilic. Thus, these reagents can be added to any standard cleavage cocktail used in peptide synthesis. The p -methoxybenzyl group of selenocysteine is easily removed by DTNP. Only sub-stoichiometric amounts of DTNP are required to cause full removal of the p -methoxybenzyl group, with as little as 0.2 equivalents necessary to effect 70% removal of the protecting group. In order to remove the p -methoxybenzyl group from cysteine, 2 equivalents of DTNP and the addition of thioanisole was required to effect removal. Thioanisole was absolutely required for the reaction in the case of the sulfur-containing amino acids, while it was not required for selenocysteine. The results were consistent with thioanisole acting as a catalyst. The acetamidomethyl group of cysteine could also be removed using DTNP, but required the addition of > 15 equivalents to be effective. DTP was less robust as a deprotection reagent. We also demonstrate that this chemistry can be used in a simultaneous cyclization/deprotection reaction between selenocysteine and cysteine residues protected by p -methoxybenzyl groups to form a selenylsulfide bond, demonstrating future high utility of the deprotection method. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] Onium Salts of Amino Acids as Co-Initiators in Photoinduced Free-Radical PolymerizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Franciszek, cigalski Abstract Summary: The onium salts of selected aliphatic and aromatic amino acids were investigated as electron donors in photoinduced free radical polymerization, in conjunction with either DIBF or BP as sensitizer. The laser flash photolysis experiments unmistakably documented that the free radical formation occurs via an electron transfer reaction from the amino acid salt to the chromophore triplet state. The kinetic studies clearly showed that either the DIBF or BP onium salts of selected aliphatic and aromatic sulfur-containing amino acids exhibit a significant increase in the efficiency of free-radical polymerization of TMPTA as compared to non-sulfur-containing co-initiators and that the efficiency of all tested electron donors is only slightly dependent on the cation type coupled with co-initiators tested. Possible mechanism for the free radical photoinitiated polymerization. [source] | |||||||||||||