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首页> 外文期刊>Acta crystallographica. Section D, Structural biology >Kinetic and structural studies of the reaction of Escherichia coli dihydrodipicolinate synthase with (S)-2-bromopropionate
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Kinetic and structural studies of the reaction of Escherichia coli dihydrodipicolinate synthase with (S)-2-bromopropionate

机译：的反应动力学和结构的研究大肠杆菌dihydrodipicolinate合酶与2-bromopropionate(年代)

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摘要

Dihydrodipicolinate synthase (DHDPS) catalyzes the first committed step in the lysine-biosynthetic pathway converting pyruvate and l-aspartate-beta-semialdehyde to dihydrodipicolinate. Kinetic studies indicate that the pyruvate analog (S)-2-bromopropionate inactivates the enzyme in a pseudo-first-order process. An initial velocity pattern indicates that (S)-2-bromopropionate is a competitive inhibitor versus pyruvate, with an inhibition constant of about 8 mM. Crystals of DHDPS complexed with (S)-2-bromopropionate formed in a solution consisting of 50 mM HEPES pH 7.5, 18% polyethylene glycol 3350, 8 mM spermidine, 0.2 M sodium tartrate and 5.0 mg ml(-1) DHDPS. The crystals diffracted to 2.15 angstrom resolution and belonged to space group P1. The crystal structure confirms the displacement of bromine and the formation of a covalent attachment between propionate and Lys161 at the active site of the enzyme. Lys161 is the active-site nucleophile that attacks the carbonyl C atom of pyruvate and subsequently generates an imine adduct in the first half-reaction of the ping-pong enzymatic reaction. A comparison of the crystal structures of DHDPS complexed with pyruvate or (S)-2-bromopropionate indicates the covalent adduct formed from (S)-2-bromopropionate leads to a rotation of about 180 degrees of the beta-delta C atoms of Lys61 that aligns the covalently bound propionate fairly closely with the imine adduct formed with pyruvate.
机译：Dihydrodipicolinate合成酶(DHDPS)催化lysine-biosynthetic承诺的第一步通路将丙酮酸和l-aspartate-beta-semialdehyde来dihydrodipicolinate。模拟(S) 2-bromopropionate丙酮酸符合一级使酶失去活性的过程。(S) 2-bromopropionate是竞争力抑制剂与丙酮酸,抑制常数约8毫米。DHDPS晶体包裹着(S) 2-bromopropionate中形成的解决方案组成的50 mM消息灵通的pH值7.5,18%8毫米亚精胺,聚乙二醇3350年,0.2米酒石酸钠和5.0毫克毫升(1)DHDPS。晶体衍射为2.15埃分辨率和属于空间群P1。结构确认溴的位移和共价连接的形成丙酸与Lys161活性部位的酶。攻击的羰基碳原子的亲核试剂丙酮酸,随后生成亚胺加合物的第一个半反应乒乓球酶反应。DHDPS包裹着的晶体结构丙酮酸或2-bromopropionate表示从(S) 2-bromopropionate共价加合物形成导致大约180度的旋转beta-delta C原子的Lys61对齐丙酸共价结合相当紧密与丙酮酸亚胺加合物形成。

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