羧酸酯酶的晶体结构的荧光假单胞菌,α/β水解酶与广泛的底物特异性。
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黄金KK,歌曲港元,胫骨DH,肯塔基州,崔书记,柳橙汁,Suh西南
羧酸酯酶的晶体结构的荧光假单胞菌,α/β水解酶与广泛的底物特异性。
结构。1997年12月15日,5 (12):1571 - 84。
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9438866 (在PubMed]
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背景:一群酯酶,分为羧酸酯酶、水解羧酸酯债券相对广泛的底物特异性和可用于立体定向合成和酯的水解。其中一个羧酸酯酶的荧光假homodimeric酶,218 -残留子单元组成。它显示了一个有限序列相似性α/β水解酶家族的一些成员。尽管晶体结构的丝氨酸酯酶和脂酶已经被报道,羧酸酯酶结构信息是非常有限的。本研究是为了提供这样的信息和理解这个羧酸酯酶的底物特异性结构依据。结果:在这项研究中,羧酸酯酶的晶体结构p .荧光是由同形的替换方法和精制1.8决议。每个单元由一个中央seven-strandedβ片两侧六个α螺旋。揭示了催化三分子结构,爵士114 - 199 - 168 asp。酶与抑制剂在复杂结构的氟化phenylmethylsulfonyl也被确定和细化至2.5。的抑制剂是共价连接到Ser 114单元,与芳环占据一个疏水网站定义的脂肪族sidechains Leu23, Ile58, Ile70, Met73 Val170。 No large structural changes are observed between the free and inhibitor-bound structures. CONCLUSIONS: Carboxylesterase from P. fluorescens has the alpha/beta hydrolase fold and the Ser-His-Asp catalytic triad. The active-site cleft in each subunit is formed by the six loops covering the catalytic serine residue. Three of the active-site loops in each subunit are involved in a head-to-head subunit interaction to form a dimer; it may be these extra structural elements, not seen in other esterases, that account for the inability of carboxylesterase to hydrolyze long chain fatty acids. As a result of dimerization, the active-site clefts from the two subunits merge to form holes in the dimer. The active-site clefts are relatively open and thus the catalytic residues are exposed to the solvent. An oxyanion hole, formed by nitrogen atoms of Leu23 and Gln115, is present in both the free and inhibitor-bound structures. An open active site, as well as a large binding pocket for the acid part of substrates, in P. fluorescens carboxylesterase may contribute to its relatively broad substrate specificity.