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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Structure of an aliphatic amidase from Geobacillus pallidus RAPc8
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Structure of an aliphatic amidase from Geobacillus pallidus RAPc8

机译：从Geobacillus结构的脂肪族酰胺酶

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摘要

The amidase from Geobacillus pallidus RAPc8, a moderate thermophile, is a member of the nitrilase superfamily and catalyzes the conversion of amides to the corresponding carboxylic acids and ammonia. It shows both amide-hydrolysis and acyl-transfer activities and also exhibits stereoselectivity for some enantiomeric substrates, thus making it a potentially important industrial catalyst. The crystal structure of G. pallidus RAPc8 amidase at a resolution of 1.9 angstrom was solved by molecular replacement from a crystal belonging to the primitive cubic space group P4(2)32. G. pallidus RAPc8 amidase is homohexameric in solution and its monomers have the typical nitrilase-superfamily alpha-beta-beta-alpha fold. Association in the hexamer preserves the eight-layered alpha-beta-beta-alpha:alpha-beta-beta-alpha structure across an interface which is conserved in the known members of the superfamily. The extended carboxy-terminal tail contributes to this conserved interface by interlocking the monomers. Analysis of the small active site of the G. pallidus RAPc8 amidase suggests that access of a water molecule to the catalytic triad (Cys, Glu, Lys) side chains would be impeded by the formation of the acyl intermediate. It is proposed that another active-site residue, Glu142, the position of which is conserved in the homologues, acts as a general base to catalyse the hydrolysis of this intermediate. The small size of the substrate-binding pocket also explains the specificity of this enzyme for short aliphatic amides and its asymmetry explains its enantioselectivity.
机译：酰胺酶从Geobacillus pallidus RAPc8,中度嗜热生物的一员腈水解酶总科和催化转换相应的酰胺羧酸和氨。amide-hydrolysis acyl-transfer活动也为一些展品立体选择性对映体基质,从而使它成为潜在的重要的工业催化剂。晶体结构的g . pallidus RAPc8酰胺酶1.9埃的决议是解决从晶体属于分子置换原始立方空间群P4(2) 32。pallidus RAPc8酰胺酶homohexameric解决方案及其单体的典型nitrilase-superfamily alpha-beta-beta-alpha褶皱。六聚体保留了协会培育alpha-beta-beta-alpha: alpha-beta-beta-alpha结构在一个接口是守恒的在已知的总科的成员。carboxy-terminal尾巴有助于延长这种守恒的接口通过联锁单体。的g . pallidus RAPc8酰胺酶表明水分子的催化三分子的访问(半胱氨酸、Glu、赖氨酸)侧链会阻碍酰基的中间的形成。提出另一个活性位点残基,Glu142的位置,这是守恒的同系物,充当一般催化这中间的水解。substrate-binding口袋的大小解释了这种酶的特异性脂肪族酰胺及其不对称的解释道选择性。

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