Cysteine conjugate beta-lyase.

Cysteine conjugate beta-lyase from rat liver, an enzyme participating in a shunt from mercapturic acid synthesis, has been purified and found to be active with a number of compounds that bear nonpolar leaving groups on the beta-carbon of an amino acid substrate. Pyridoxal phosphate is considered to be a participant in the reaction. In addition to aromatic thioethers of cysteine, the enzyme is also active with two aliphatic amino acid derivatives, S-1,2-dichlorovinyl-L-cysteine and beta-chloroalanine. Evidence is presented that catalysis results in "suicide" inhibition with a partition ratio of about 600 for each of the substrates.