副球菌denitrificans芳香族氨基酸转氨酶:一个模型研究酶的双底物识别机制。
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我们的年代,Okamoto, Nakai Y, Nakahira M, Shibatani T, Hayashi H, Kagamiyama H
副球菌denitrificans芳香族氨基酸转氨酶:一个模型研究酶的双底物识别机制。
,1997年1月,121 (1):161 - 71。
- PubMed ID
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9058208 (在PubMed]
- 文摘
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芳香族氨基酸转氨酶的基因(ArAT)副球菌denitrificans克隆,测序,在大肠杆菌细胞中过表达。序列不同于先前报道[高木涉,T。谷口,T。山本,Y。,Shibatani t生物科技(1991)》。达成。。13日,112 - 119]。酶(pdArAT)纯化同质性,和特征。这是类似于天冬氨酸转氨酶(AspAT)和ArAT大肠杆菌(ecArAT)在许多方面,包括总蛋白质结构和光谱性质。pdArAT显示活动向二元羧酸和芳香基质,和分析底物类似物的绑定和quasisubstrates酶表明,二元羧酸和芳香基质采取类似取向pdArAT的活性部位;这些属性与ecArAT本质上是一样的。对于ecArAT,中性氨基酸pdArAT具备较大的侧链的基质,这表明衬底之间的疏水作用和酶对底物的识别是重要的中性侧链。 pdArAT catalyzed transamination of phenylalanine and tyrosine far more efficiently (10(2)-fold in terms of kcat/Km) than those of straight-chain aliphatic amino acids with similar side-chain surface area, whereas ecArAT did not show significant preference for aromatic amino acids over aliphatic amino acids. This shows that the substrate-side-chain-binding pocket of pdArAT, as compared with the pocket of ecArAT, is well suited in shape for interaction with the phenyl and hydroxyphenyl rings of substrates. Thus, pdArAT is an ideal enzyme among ArATs for the study of the high-specificity recognition of two different kinds of substrates, the one having a carboxylic side chain and the other having an aromatic side chain.