首页> 外文OA文献 >Structure of 3,4-Dihydroxy-2-butanone 4-Phosphate Synthase from Methanococcus jannaschii in Complex with Divalent Metal Ions and the Substrate Ribulose 5-Phosphate: implications for the catalytic mechanism
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Structure of 3,4-Dihydroxy-2-butanone 4-Phosphate Synthase from Methanococcus jannaschii in Complex with Divalent Metal Ions and the Substrate Ribulose 5-Phosphate: implications for the catalytic mechanism

机译:詹氏甲烷球菌3,4-二羟基-2-丁酮4-磷酸合酶与二价金属离子和5-磷酸核糖底物复合的结构:对催化机理的影响

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摘要

Skeletal rearrangements of carbohydrates are crucial for many biosynthetic pathways. In riboflavin biosynthesis ribulose 5-phosphate is converted into 3,4-dihydroxy-2-butanone 4-phosphate while its C4 atom is released as formate in a sequence of metal-dependent reactions. Here, we present the crystal structure of Methanococcus jannaschii 3,4-dihydroxy-2-butanone 4-phosphate synthase in complex with the substrate ribulose 5-phosphate at a dimetal center presumably consisting of non-catalytic zinc and calcium ions at 1.7-Å resolution. The carbonyl group (O2) and two out of three free hydroxyl groups (OH3 and OH4) of the substrate are metal-coordinated. We correlate previous mutational studies on this enzyme with the present structural results. Residues of the first coordination sphere involved in metal binding are indispensable for catalytic activity. Only Glu-185 of the second coordination sphere cannot be replaced without complete loss of activity. It contacts the C3 hydrogen atom directly and probably initiates enediol formation in concert with both metal ions to start the reaction sequence. Mechanistic similarities to Rubisco acting on the similar substrate ribulose 1,5-diphosphate in carbon dioxide fixation as well as other carbohydrate (reducto-) isomerases are discussed.
机译:碳水化合物的骨架重排对于许多生物合成途径至关重要。在核黄素的生物合成中,核糖5-磷酸转化为3,4-二羟基-2-丁酮4-磷酸,而其C4原子在一系列金属依赖性反应中作为甲酸盐释放。在这里,我们介绍了甲烷双球菌3,4-二羟基-2-丁酮4-磷酸合酶与底物核糖5-磷酸在双金属中心的复合晶体结构,该金属可能由非催化的锌和钙离子组成,位于1.7-Å解析度。底物的羰基(O2)和三个游离羟基中的两个(OH3和OH4)是金属配位的。我们将这种酶的先前突变研究与目前的结构结果相关联。涉及金属结合的第一配位球的残留对于催化活性是必不可少的。在没有完全丧失活动的情况下,只有第二个协调领域的Glu-185才能被取代。它直接与C3氢原子接触,并可能与两种金属离子一起引发烯二醇的形成,从而开始反应序列。讨论了与Rubisco在二氧化碳固定中作用于相似底物核糖1,5-二磷酸核糖以及其他碳水化合物(还原)异构酶的机理相似性。

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