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首页> 外文期刊>Biochemistry >New superfamily members identified for Schiff-base enzymes based on verification of catalytically essential residues
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New superfamily members identified for Schiff-base enzymes based on verification of catalytically essential residues

机译：新的超家族成员基于对催化基本残基的验证而鉴定为席夫碱酶

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摘要

Enzymes that utilize a Schiff-base intermediate formed with their substrates and that share the same alpha/beta barrel fold comprise a mechanistically diverse superfamily defined in the SCOPS database as the class I aldolase family. The family includes the "classical" aldolases fructose-1,6-(bis) phosphate (FBP) aldolase, transaldolase, and 2-keto-3-deoxy-6-phosphogluconate aldolase. Moreover, the N-acetylneuraminate lyase family has been included in the class I aldolase family on the basis of similar Schiff-base chemistry and fold. Herein, we generate primary sequence identities based on structural alignment that support the homology and reveal additional mechanistic similarities beyond the common use of a lysine for Schiff-base formation. The structural and mechanistic correspondence comprises the use of a catalytic dyad, wherein a general acid/base residue (Glu, Tyr, or His) involved in Schiff-base chemistry is stationed on beta-strand 5 of the alpha/beta barrel. The role of the acid/base residue was probed by site-directed mutagenesis and steady-state and pre-steady-state kinetics on a representative member of this family, FBP aldolase. The kinetic results are consistent with the participation of this conserved residue or position in the protonation of the carbinolamine intermediate and dehydration of the Schiff base in FBP aldolase and, by analogy, the class I aldolase family.
机译：利用与底物形成的席夫碱中间体并共享相同的α/β桶折叠的酶包括在机械上多样化的超家族，在SCOPS数据库中定义为I类醛缩酶家族。该家族包括“经典”醛缩酶果糖-1，6-（双）磷酸（FBP）醛缩酶，反式醛缩酶和2-酮-3-脱氧-6-磷酸葡糖醛酸醛缩酶。而且，基于相似的席夫碱化学性质和折叠，N-乙酰神经氨酸裂合酶家族已被包括在I类醛缩酶家族中。在本文中，我们基于结构比对产生了支持同源性的主要序列同一性，并揭示了除了赖氨酸用于Schiff碱基形成的常见用途之外的其他机制相似性。结构和机理上的对应关系包括使用催化二联体，其中参与席夫碱化学反应的一般酸/碱残基（Glu，Tyr或His）位于α/β桶的β链5上。酸/碱残基的作用通过定点诱变以及该家族中代表性成员FBP醛缩酶的稳态和稳态前动力学来探测。动力学结果与该保守残基或位置参与甲醇酚中间体的质子化和FBP醛缩酶中的席夫碱的脱水以及类似地，属于I类醛缩酶家族一致。

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