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The Primitive Protozoon Trichomonas vaginalisContains Two Methionine γ-Lyase Genes That Encode Members of the γ-Family of Pyridoxal 5′-Phosphate-dependent Enzymes
Journal article   Open access   Peer reviewed

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

Amanda E. McKie, Thomas Edlind, John Walker, Jeremy C. Mottram, Graham H. Coombs and Joseph D Walker
The Journal of biological chemistry, v 273(10), pp 5549-5556
06 Mar 1998
DOI: https://doi.org/10.1074/jbc.273.10.5549
Featured in Collection :   UN Sustainable Development Goals @ Drexel
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https://doi.org/10.1074/jbc.273.10.5549View
Published, Version of Record (VoR)CC BY V4.0,  Open

Abstract

Methionine γ-lyase, the enzyme that catalyzes the breakdown of methionine by an α,γ-elimination reaction and is a member of the γ-family of pyridoxal 5′-phosphate-dependent enzymes, is present in high activity in the primitive protozoan parasite Trichomonas vaginalisbut is absent from mammals. Two genes, mgl1 and mgl2, encoding methionine γ-lyase, have now been isolated from T. vaginalis. They are both single copy, encode predicted proteins (MGL1 and MGL2) of 43 kDa, have 69% sequence identity with each other, and show a high degree of sequence identity to methionine γ-lyase from Pseudomonas putida (44%) and other related pyridoxal 5′-phosphate-dependent enzymes such as human cystathionine γ-lyase (42%) and Escherichia coli cystathionine β-lyase (30%). mgl1 and mgl2 have been expressed in E. coli as a fusion with a six-histidine tag and the recombinant proteins (rMGL1 and rMGL2) purified by metal-chelate affinity chromatography. rMGL1 and rMGL2 were found to have high activity toward methionine (10.4 and 0.67 μmol/min/mg of protein, respectively), homocysteine (370 and 128 μmol/min/mg of protein), cysteine (6.02 and 1.06 μmol/min/mg of protein), and O-acetylserine (3.74 and 1.51 μmol/min/mg of protein), but to be inactive toward cystathionine. Site-directed mutagenesis of an active site cysteine (C113G for MGL1 and C116G for MGL2) reduced the activity of the recombinant enzymes toward both methionine and homocysteine by approximately 80% (rMGL1) and 90% (rMGL2). In contrast, the activity of mutated rMGL2 toward cysteine and O-acetylserine was increased (to 214 and 142%, respectively), whereas that of mutated rMGL1 was reduced to 39 and 49%, respectively. These findings demonstrate the importance of this cysteine residue in the α,β-elimination and α,γ-elimination reactions catalyzed by trichomonad methionine γ-lyase.

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Domestic collaboration
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Web of Science research areas
Biochemistry & Molecular Biology
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