Purification and characterization of cystathionine γ-liase from Lactobacillus fermentum DT41

A homo-tetrameric ca. 140-kDa cystathionine y-lyase was purified to homogeneity from Luctobacillus,f~rmentum DT41 by four chromatographic steps. This was the first enzyme responsible for amino acid catabolism purified from lactobacilli. The activity is pyridoxal-5’-phosphate d pendent and the enzyme catalyzes the a,y-elimination reaction of L-cystathionine producing L-cysteine, ammonia and a-ketobutyrate. The cystathionine y-lyase produced a free thiol group, a keto acid component and ammonia from several amino acids, including L-cysteine and methionine, and amino acid derivatives. L-Cystine was the best substrate. The enzyme was stable in the conditions of cheese ripening and may contribute to the biosynthesis o