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In enzymology, a methylglyoxal synthase () is a enzyme that catalyzes the chemical reaction :dihydroxyacetone phosphate methylglyoxal + phosphate Hence, this enzyme has one substrate, DHAP, and two products, methylglyoxal and phosphate. Attempts to observe reversibility of this reaction have been unsuccessful. This enzyme belongs to the family of lyases, specifically those carbon-oxygen lyases acting on phosphates. The systematic name of this enzyme class is glycerone-phosphate phosphate-lyase (methylglyoxal-forming). Other names in common use include methylglyoxal synthetase, and glycerone-phosphate phospho-lyase. This enzyme participates in pyruvate metabolism and is constitutively expressed.〔 ==Structural Studies== As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , and . Methylglyoxal synthase (MGS) is a 152-amino acid homohexamer that has a molecular weight of approximately 67,000 kD. The total solvent-accessible surface area of the MGS homohexamer is 18,510 square Angstroms, roughly 40% of the total possible surface area if the subunits were separated.〔 Each monomer consists of five alpha helices surrounding five beta sheets. Of these, two antiparallel beta sheets and one alpha helix are located in a subdomain where the N-terminus and C-terminus are in close juxtaposition.〔 The homohexamer exhibits a threefold axis perpendicular to a twofold axis. Within the wide V-groove, there are twelve hydrogen bonds and six salt bridges between the monomers in the presence of phosphate binding. In the absence of phosphate binding, ten hydrogen bonds and two salt bridges hold the monomers together. At the peak interfaces, ten hydrogen bonds and no salt bridges connect the monomers regardless of phosphate binding.〔 The MGS homohexamer is slightly asymmetrical. All three monomers within the asymmetrical region contain a formate molecule within their respective actives sites. Only one of the monomers within the asymmetrical region is additionally bound to a phosphate.〔 The active site contains many conserved residues for function (Asp, His, Thr) and structure (Gly, Pro). Inorganic phosphate interacts with Lys23, Thr45, Thr47, Thr48, and Gly66. Formate interacts with His19, His98, and Asp71. The active site is exposed to the solvent via a perpendicular channel that consists of Arg150, Tyr146, Asp20, Pro67, His98, and His19.〔 Although mechanistically similar to triosephosphate isomerase (TIM), MGS contains widely dissimilar protein folding that prevents structural alignment with TIM which suggests convergent evolution of their chemical reactions. However, Asp71 in MGS may act similarly to the Glu165, the catalytic base in TIM. Additionally, His19 and His98 may perform the role of the electrophilic catalyst similar to His95 in TIM. CheB methylesterase has the highest structural similarity with MGS.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Methylglyoxal synthase」の詳細全文を読む スポンサード リンク
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