Purification and characterization of cystathionine γ-lyase fromLactobacillus fermentumDT41

Abstract

A homo-tetrameric ca. 140-kDa cystathionine γ-lyase was purified to homogeneity from Lactobacillus fermentum DT41 by four chromatographic steps. This was the first enzyme responsible for amino acid catabolism purified from lactobacilli. The activity is pyridoxal-5′-phosphate dependent and the enzyme catalyzes the α,γ-elimination reaction of l-cystathionine producing l-cysteine, ammonia and α-ketobutyrate. The cystathionine γ-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 of sulfur-containing compounds.