The Primitive Protozoon Trichomonas vaginalisContains Two Methionine γ-Lyase Genes That Encode Members of the γ-Family of Pyridoxal 5′-Phosphate-dependent Enzymes

摘要: Methionine gamma-lyase, the enzyme that catalyzes breakdown of methionine by an alpha,gamma-elimination reaction and is a member gamma-family pyridoxal 5'-phosphate-dependent enzymes, present in high activity primitive protozoan parasite Trichomonas vaginalis but absent from mammals. Two genes, mgl1 mgl2, encoding have now been isolated T. vaginalis. They are both single copy, encode predicted proteins (MGL1 MGL2) 43 kDa, 69% sequence identity with each other, show degree to gamma-lyase Pseudomonas putida (44%) other related enzymes such as human cystathionine (42%) Escherichia coli beta-lyase (30%). mgl2 expressed E. fusion six-histidine tag recombinant (rMGL1 rMGL2) purified metal-chelate affinity chromatography. rMGL1 rMGL2 were found toward (10.4 0.67 mumol/min/mg protein, respectively), homocysteine (370 128 protein), cysteine (6.02 1.06 O-acetylserine (3.74 1.51 be inactive cystathionine. Site-directed mutagenesis active site (C113G for MGL1 C116G reduced approximately 80% (rMGL1) 90% (rMGL2). In contrast, mutated was increased (to 214 142%, whereas 39 49%, respectively. These findings demonstrate importance this residue alpha,beta-elimination alpha, gamma-elimination reactions catalyzed trichomonad gamma-lyase.