Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Biochemistry (Mosc). 2011 Apr;76(4):480-90. doi: 10.1134/s0006297911040122.
Enzymatic properties of a novel oligopeptidase B from psychrotolerant gram-negative microorganism Serratia proteamaculans (PSP) were studied. The substrate specificity of PSP was analyzed using p-nitroanilide substrates, and the influence of calcium ions on the enzyme activity was studied. Hydrolysis of oligopeptides by PSP was studied using melittin as the substrate. Optimal conditions for the PSP activity (pH and temperature) have been established. It was found that PSP shares some properties with oligopeptidases B from other sources containing two Asp/Glu residues in the S2 site, but it differs significantly in some characteristics. The S2 site of PSP contains only one Asp460 residue. The secondary specificity of PSP has a number of specific features: an unusual substrate inhibition by peptides with hydrophobic residues at the P2 position, as well as the drastic influence of calcium ions on substrate characteristics of the enzyme. It is assumed that the PSP molecule contains a large hydrophobic substrate-binding site, and significant conformational rearrangements of the enzyme active site are induced by Ca(2+) binding and by the formation of the enzyme-substrate complex. The temperature characteristics of PSP (high activity at low temperature as well as low apparent temperature optimum (25°C)) confirm that PSP is a psychrophilic enzyme.
研究了耐冷革兰氏阴性微生物沙雷氏菌（Serratia proteamaculans，PSP）新型寡肽酶 B 的酶学性质。使用对硝基苯胺底物分析了 PSP 的底物特异性，并研究了钙离子对酶活性的影响。使用蜂毒素作为底物研究了 PSP 对寡肽的水解作用。确定了 PSP 活性的最佳条件（pH 和温度）。结果表明，PSP 与其他来源的寡肽酶 B 具有一些共同特性，S2 位含有两个 Asp/Glu 残基，但在某些特性上存在显著差异。PSP 的 S2 位仅含有一个 Asp460 残基。PSP 的二级特异性具有许多特定特征：在 P2 位具有疏水性残基的肽对底物具有异常的抑制作用，以及钙离子对酶底物特性的剧烈影响。据推测，PSP 分子含有一个大的疏水性底物结合位点，Ca(2+)结合和酶-底物复合物的形成诱导酶活性位点的显著构象重排。PSP 的温度特性（低温下活性高，表观最适温度（25°C）低）证实了 PSP 是一种嗜冷酶。
