ACTIVE-CENTERS OF STREPTOMYCES-GRISEUS PROTEASE-3, ALPHA-CHYMOTRYPSIN, AND ELASTASE - ENZYME-SUBSTRATE INTERACTIONS CLOSE TO SCISSILE BOND
ACTIVE-CENTERS OF STREPTOMYCES-GRISEUS PROTEASE-3, ALPHA-CHYMOTRYPSIN, AND ELASTASE - ENZYME-SUBSTRATE INTERACTIONS CLOSE TO SCISSILE BOND
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DOI：
10.1021/bi00651a020
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发表时间：
1976-01-01
期刊：
影响因子：
2.9
通讯作者：
BLOUT, ER
中科院分区：
文献类型：
--
作者：
BAUER, CA;THOMPSON, RC;BLOUT, ER
报道了食糜-胰蛋白酶-，灰色链霉菌蛋白酶3 (SGP3)-和弹性酶催化水解许多肽的动力学常数。与胰凝乳酶一样，sp3最容易水解酰胺键，其直接酰基（Pi）是一个大的疏水氨基酸残基。然而，与胰凝乳蛋白酶相比，SGP3对Pi残基具有更广泛的特异性，这主要是因为SGP3与底物残基Pi之间最重要的相互作用涉及P]侧链的Cp和C7基团。对于所有三种蛋白酶的底物，我们目前对蛋白水解酶的了解可以通过它们与形成底物的键的两个氨基酸残基的相互作用来理解。这些相互作用是酶的主要特异性的基础。最近，很明显，这些酶经常与底物的其他氨基酸残基相互作用，导致“二级特异性”（Fru-ton, 1975），长肽比短肽水解得更快。之前的文章（Bauer et al., 1976）描述了a-chymotrypsin和Streptomyces griseus蛋白酶3 （sp3）的二级特异性1。为了确定这些酶的次级特异性和初级特异性之间的关系，我们还研究了一些酶-底物相互作用，这些相互作用表现在凝乳胰蛋白酶SGP3和相关丝氨酸蛋白酶胰腺弹性酶的初级特异性中。众所周知，胰糜蛋白酶水解酰基（Pi） 2为芳香氨基酸的肽键速度最快，从酶-底物复合物的结构来看，这种特异性得到了很好的理解（Blow, 1971）。弹性蛋白酶水解酰基为小疏水氨基酸的键的特异性也得到了很好的证实（Geneste and Bender, 1969; Kaplan et al., 1970; Thompson and Blout, 1973），并且已经提出了这种特异性的结构基础（Hartley and Shotton, 1971; Shotton et al., 1972）。相比之下，SGP3的主要特异性既未确定，也未从结构角度理解。本文将报道胰凝乳蛋白酶和SGP3的主要特异性的比较，并提出这两种酶的S′-Pi接触结构可能存在差异的方式。
Kinetic constants are reported for-chymo-trypsin-, Streptomyces griseus protease 3 (SGP3)-, and elastase-catalyzed hydrolysis of a number of peptides. SGP3, like-chymotrypsin, hydrolyzes most readily amide bonds whose immediate acyl group (Pi) is a large, hydrophobic, amino acid residue. SGP3, however, has a broader specificity for Pi residues than does-chymotrypsin, primarily be-cause the most important interactions between SGP3 and residue Pi of the substrate involve the Cp and C7 groups of the P] side chain. For substrates of all three proteases, theIViuch of our current knowledge of proteolytic enzymes can be understood in terms of their interactions with the two amino acid residues which form thescissile bond of the substrate. These interactions are the basis of the enzymes’ primary specificity. Recently, it has become apparent that these enzymes often interact with other amino acid residues of the substrate, leading to a “secondary specificity”(Fru-ton, 1975), with long peptides being hydrolyzed more rapidly than short ones. The preceding paper (Bauer et al., 1976) described the secondary specificity of both a-chymotrypsin and Streptomyces griseus Protease 3 (SGP3) 1. To determine the relationship between secondary and primary speci-ficity in these enzymes, we have also studied some of the en-zyme-substrate interactions manifested inthe primary specificity of-chymotrypsin, SGP3, and a related serine protease, pancreatic elastase.-Chymotrypsin is known to hydrolyze most rapidly pep-tide bonds whose acyl group (Pi) 2 is an aromatic amino acid, and this specificity is well-understood in terms of the structure of the enzyme-substrate complex (Blow, 1971). The specificity of elastase for hydrolyzing bonds whose acyl group is a small hydrophobic amino acid is also well-estab-lished (Geneste and Bender, 1969; Kaplan et al., 1970; Thompson and Blout, 1973b), and a structural basis for this specificity has been presented (Hartley and Shotton, 1971; Shotton et al., 1972). In contrast, the primary specificity of SGP3 is neither well-established nor is it understood in structural terms. This communication will report a compar-ison of the primary specificity of-chymotrypsin and SGP3 and suggest ways in which the structure of the S¡—Pi con-tact might be expected to differ in these two enzymes.