3 DIMENSIONAL STRUCTURE OF PORCINE PANCREATIC ALPHA-AMYLASE AT 2.9 A RESOLUTION - ROLE OF CALCIUM IN STRUCTURE AND ACTIVITY
3 DIMENSIONAL STRUCTURE OF PORCINE PANCREATIC ALPHA-AMYLASE AT 2.9 A RESOLUTION - ROLE OF CALCIUM IN STRUCTURE AND ACTIVITY
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DOI：
10.1002/j.1460-2075.1987.tb02731.x
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发表时间：
1987-12-01
期刊：
影响因子：
11.4
通讯作者：
PAYAN, F
中科院分区：
文献类型：
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作者：
BUISSON, G;DUEE, E;PAYAN, F
猪胰α-淀粉酶的晶体结构淀粉酶（PPA）已溶解为2.9 °。通过X射线晶体学方法的分辨率。该酶含有三个结构域。较大的，在N-末端部分，由330个氨基酸残基组成。该中心结构域具有典型的平行链α sbd β桶结构（α sbd β barrel structure）。beta.）8，已经在许多其他酶如磷酸丙糖异构酶和丙酮酸激酶中发现。C-末端结构域形成独特的球状单元，其中链折叠成八链反平行β-链。每桶第三个域位于β-链和α-在磷酸丙糖异构酶和丙酮酸激酶中结构域B的类似位置。它基本上由反平行的β-薄膜.活性位点位于N-末端中心结构域内的裂缝中，在β-半胱氨酸的羧基末端。（α.. beta.）8桶。各种底物类似物与酶的结合表明，参与催化反应的氨基酸残基是一对天冬氨酸。许多其他残基围绕底物，似乎通过氢键和疏水相互作用参与其结合。“必需的”钙离子位于活性位点区域附近和两个结构域之间，每个结构域提供两个钙配体。在序列比较的基础上，该钙结合位点被认为是所有α-淀粉酶 它代表了一种新型的钙-蛋白相互作用模式。此外，与本模型可以合理的钙离子在确定最佳酶活性所需的三级结构的重要性。
The crystal structure of porcine pancreatic .alpha.-amylase (PPA) has been solved at 2.9 .ANG. resolution by X-ray crystallographic methods. The enzyme contains three domains. The larger, in the N-terminal part, consists of 330 amino acid residues. This central domain has the typical parallel-stranded alpha.sbd.beta barrel structure (.alpha..beta.)8, already found in a number of other enzymes like triose phosphate isomerase and pyruvate kinase. The C-terminal domain forms a distinct globular unit where the chain folds into an eight-stranded antiparallel .beta.-barrel. The third domain lies between a .beta.-strand and a .alpha.-helix of the central domain, in a position similar to those found for domain B in triose phosphate isomerase and pyruvate kinase. It is essentially composed of antiparallel .beta.-sheets. The active site is located in a cleft within the N-terminal central domain, at the carboxy-end of the .beta.-strands of the (.alpha..beta.)8 barrel. Binding of various substrate analogues to the enzyme suggests that the amino acid residues involved in the catalytic reaction are a pair of aspartic acids. A number of other residues surround the substrate and seem to participate in its binding via hydrogen bonds and hydrophobic interactions. The ''essential'' calcium ion has been located near the active site region and between two domains, each of them providing two calcium ligands. On the basis of sequence comparisons this calcium binding site is suggested to be a common structural feature of all .alpha.-amylases. It represents a new type of calcium.sbd.protein interaction pattern. Moreover with the present model one can rationalize the importance of the calcium ion in determining the tertiary structure required for optimal enzymatic activity.