Distribution of two kinds of cystathionine γ-synthase in various bacteria

The substrate specificity of cystathionine γ-synthase (EC 4.2.99.9) in various bacteria was examined.O-Succinyl-l-homoserine was used preferably as a substrate by facultative anaerobic Gram-negative bacteria belonging to such genera asEscherichia, Klebsiella, Enterobacter, Citrobacter, Erwinia, Serratia, Proteus andSalmonella. Among Gram-negative aerobic bacteria, bacteria belonging to the generaPseudomonas, Xanthomonas andAlcaligenes also usedO-succinyl-l-homoserine in preference toO-acetyl-l-homoserine. On the other hand, bacteria belonging to the generaAgrobacterium andFlavobacterium usedO-acetyl-l-homoserine preferably. As to Gram-positive aerobic bacteria, bacteria of the genusBacillus usedO-acetyl-l-homoserine exclusively. Bacteria belonging to the generaMicrococcus, Corynebacterium, Brevibacterium andArthrobacter used bothO-acetyl- andO-succinyl-l-homoserine to similar extents.