Oxidative deamination of carboxyethyl-cysteine and carboxymethyl-homocysteine.
Snake venom L-aminoacid oxidase, while inactive on 4C and 5C dicarboxylic alpha-amino acids, may oxidize their 6C and 7C homologues alpha-aminoadipic and alpha-aminopimelic acid. It has been demonstrated that the enzyme also oxidizes S-carboxyethyl-L-cysteine and S-carboxymethyl-L-homocysteine, two analogues of alpha-aminopimelic acid with the gamma or delta methylene groups substituted by a sulfur atom. As oxidation products the corresponding ketoacids were obtained. Thus substrate specificity of L-aminoacid oxidase for dicarboxylic alpha-aminoacids seems highly dependent on the carbon chain length, whereas substitution of a methylene group by a sulfur atom seems to have almost no effect. On the other hand, D-aspartate oxidase from beef kidney (active on 4C to 6C dicarboxylic alpha-aminoacids) cannot oxidize the 7C alpha-aminopimelic acid but is active on the S-carboxyethyl-D-cysteine analogue. The other aminopimelic analogue, S-carboxymethyl-D-homocysteine, is a very poor substrate. Thus the substrate specificity of D-aspartate oxidase, highly dependent on chain length, is also influenced by chain conformation. Furthermore, oxidation of either compound under study, L-aminoacid oxidase and D-aspartate oxidase, leaves unaffected the thioether bond.
D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D002233:Carbocysteine / Q000031:analogs & derivatives*; D003435:Crotalid Venoms / Q000378:metabolism*; D003545:Cysteine / Q000031:analogs & derivatives*; D007700:Kinetics; D010084:Oxidation-Reduction; D010101:Oxygen Consumption
D003435:Crotalid Venoms; D002233:Carbocysteine; D000594:Amino Acid Oxidoreductases; D003545:Cysteine