C-S-lyase

Rossol I, A Ptihler (1992) The Corynebacterium glutamicum aecD gene encodes a C-S lyase with alpha-beta-elimination activity that degrades aminoethylcysteine. J Bacteriol 174 2968-2977. 

Yoshida Y, Y Nakano, A Amano, M Yoshimura, H Fukamachi, T Oho, Y Koga (2002) led from Streptoccus anginosus encodes a C-S lyase with a,P-elimination activity that degrades L-cysteine. Microbiology (UK) 148 3961-3970. 

Mushrooms have been investigated with especial reference to shiitake, Lentinus edodes, the flavorful fungus widely used in Chinese and Japanese dishes. While the umami taste is attributed to guanylic acid, lentinic acid 14 (Scheme 6) is converted to lenthionine, 1,2,3,5,6-pentathiacycloheptane 15, a compound with the characteristic shiitake flavor. This complex reaction requires a C-S lyase enzyme.30 Other important flavor compounds are 1,2,4,6-tetrathiacycloheptane 16 (Scheme 6) and 1,2,3,4,5,6-hexathiacycloheptane (not shown). 

Lenthionine has the characteristic shiitake flavor. It is formed from the precursor, lentinic acid 14 by complex reactions involving a C-S lyase enzyme.30 Cyclic polysulfides occur in other Basidiomycete mushrooms (Genus Micromp-hale and Colly bid), in some red alga, and in seeds of Parkia speciosa. The latter contain lenthionine and 1,2,4-trithiolane (1,2,4-trithiacyclopentane) 17 as well as compounds with 4, 5, or 6 sulfur atoms.31 These seeds are valued in Indonesia for a unique, onion-like odor. Djenkolic acid and dichrostachinic acid S -[(2-carboxy-2-hydroxyethylsulfonyl)-methyl]cysteine are converted by a C-S lyase enzyme to cyclic polysulfides djenkolic acid yields 1,2,4-trithiolane and 1,2,4,6-tetrathiepane the latter is also formed from dichrostachinic acid.32... 

For DMS and DMTS, S-mothyl-L-cysteine sulfoxide is a precursor action of a C-S lyase enzyme yields methanesulfenic acid, CH3-S-OH, and hence methyl methanethiosulfinate, CH3-SO-S-CH3. Disproportionation reactions yield polysulfides such as DMS.56... 

KIDDLE, G.A., BENNETT, R.N., HICK, A.J., WALLSGROVE, R.M., C-S lyase activities in leaves of crucifers and non-crucifers, and the characterzation of three classes of C-S lyase activities from oilseed rape (Brassica napus L.), Plant, Cell and Environment, 1999, 22, 433-445. 

SCHWIMMER, S., KJAER, A., Purification and specificity of the C-S lyase of Albizzia lophanta, Biochim. Biophys. Acta, 1960, 42, 316-324. 

Clausen T, Kaiser JT, Steegborn C, et al. 2000. Crystal structure of the cystine C-S lyase from Synechocystis stalibization of cysteine persulfide for FeS cluster biosynthesis. Proc Natl Acad Sci USA 97 3856-61. 

The immediate precursor of pentachlorothiophenol was assumed to be S-(PCP)Cys. Cysteine C-S lyase enzymes that convert S-aryl and S-alkyl derivatives of cysteine to pyruvate and a thioalcohol have been detected in some plant species (24,. When the... 

Pentachlorothiophenol was formed Iji vitro from S-(PCP)Cys by a C-S lyase enzyme from onion root. This enzyme was active with S-(PCP)Cys, S-(2,M-dinitrophenyl)cysteine, and the cysteine conjugate of propachlor. A C-S lyase from Alblzzla lophanta was previously shown to utilize a broad range of cysteine derivatives (2U). 

Insoluble residue was the most abundant product of penta-chlorothiophenol metabolism in peanut. The importance of this process is obviously dependent upon the presence of an active C-S lyase system. S-(Pentachlorophenyl)cysteine was also a precursor of insoluble residue in peanut, but the extent to which this involved pentachlorothlophenol as an intermediate was not determined. Additional studies are needed to determine if insoluble residues are commonly formed from GSH conjugates by other routes. 

Evidence was also provided that Insoluble residues may be produced from GSH conjugates via cysteine conjugate or thiol Intermediates. These studies also suggested that certain reactions should be studied in greater detail to assess their importance in pesticide metabolism l.e., the C-S lyase reaction, the methyl transferase reaction, and the transamination reaction. 

We have not determined where the S-methylation of the C-S lyase cleavage products occurs. It could take place in the flora, although no 2-methylthio acetanilides were detected in the pig cecal content incubations, and no methylthio-, or methylsulfonyl-containing N-isopropylacetanilides were extractable from any rat feces. The conventional rat feces contained only nonextractable residues. The methylation could also take place in the tissues upon or after absorption of the intestinal metabolites because thiol S-methyltransferase is present in... 

Pentachloromethylthiobenzene (PCMTB) is metabolized in rats to bis-(methylthio)tetrachlorobenzene (bis-MTTCB) by a microflora dependent pathway that involves biliary excretion of the mercapturate precursors and the action of a microfloral C-S lyase (8). The results of metabolism studies in rats are outlined in table III. Eighty-one percent of single oral doses of labeled PCMTB were excreted with the feces as bis-MTTCB and nonextractable residues in about equal amounts. Germfree rats excreted about 88 percent of the dose with the feces as at least two mercapturic acids (I, II, fig. 3 ). The major metabolite in the urine from both conventional and germfree rats was the mercapturic acid. 

As in the case of propachlor mercapturic acid sulfoxide, the biological significance of xenobiotic mercapturic acids that contain oxidized sulfur is not known. Casida et al. (39) have reported that sulfoxidation of some thiocarbamate herbicides is a beneficial step in the detoxication process. However, cysteine conjugates can exhibit adverse biological activities. Smith (40) has reviewed work on the metabolism of the toxic principle in kale and has shown that C-S lyase action on S-methylcysteine sulfoxide produces the toxic principle. Virtanen ( ) has reviewed the processes in other plants that lead to the production of compounds with biological activity from -substituted cysteine sulfoxides. 

Catabolism Utilizing Tissue C-S Lyases And Microfloral S-Glucuronidases In Addition To The Microfloral C-S Lyase... 

Metabolic activation. Although the kidney does not contain as much cytochromes P-450 as the liver, there is sufficient activity to be responsible for metabolic activation, and other oxidative enzymes such as those of the prostaglandin synthetase system are also present. Such metabolic activation may underlie the renal toxicity of chloroform and paracetamol (see chap. 7). Other enzymes such as C-S lyase and GSH transferase may also be involved in the activation of compounds such as hexachlorobutadiene (see chap. 7). In some cases, hepatic metabolism may be involved followed by transport to the kidney and subsequent toxicity. 

The reactive thiol/thioketene produced by the (3-lyase is an alkylating fragment, which binds to protein, DNA, and GSH. The fact that one of the locations of C-S lyase is in mitochondria may explain why this organelle seems to be damaged. Damage to the respiratory chain will lead to depletion and a shortage of ATP, which is vitally necessary for the activity of the kidney in terms of active uptake and secretion. 

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