Simons J W, Götz F, Egmond M R, Verheij H M
Department of Enzymology and Protein Engineering, Utrecht University, The Netherlands.
Chem Phys Lipids. 1998 Jun;93(1-2):27-37. doi: 10.1016/s0009-3084(98)00026-7.
Various staphylococci secrete lipases which require calcium ions for activity, and have profound preferences for substrates with different chain lengths. The lipase from Staphylococcus hyicus is exceptional since it has higher phospholipase than lipase activity. This paper gives an overview of the biochemical properties of these enzymes. It appears that chain length selectivity of these enzymes resides in the acylation step. Interfaces mainly influence the acylation step. Calcium ions do not influence the rate of acylation or deacylation although stabilise the enzyme against denaturation. Molecular modelling based on the X-ray structure of Pseudomonas glumae lipase was used to construct a model of the staphylococcal lipases. With this model the position of serveral residues involved in stubstrate selectivity was predicted. Moreover, a sequence element could be assigned that may function as the so-called lid domain in staphylococcal lipases. Sequence alignment of four staphylococcal lipases, and lipases from P. glumae and Bacillus thermocatenulatus identified several potential calcium ligands, one of which was verified by site directed mutagensesis. It is concluded that stabilisation of lipases by calcium ions might be a more general phenomenon than recognized so far.
多种葡萄球菌分泌的脂肪酶需要钙离子来激活，并且对不同链长的底物有明显偏好。来自猪葡萄球菌的脂肪酶很特别，因为它的磷脂酶活性高于脂肪酶活性。本文概述了这些酶的生化特性。这些酶的链长选择性似乎存在于酰化步骤中。界面主要影响酰化步骤。钙离子虽然能使酶稳定不发生变性，但并不影响酰化或脱酰化的速率。基于稻谷假单胞菌脂肪酶的X射线结构进行分子建模，以构建葡萄球菌脂肪酶的模型。利用该模型预测了参与底物选择性的几个残基的位置。此外，还可以确定一个序列元件，它可能在葡萄球菌脂肪酶中起所谓的盖子结构域的作用。对四种葡萄球菌脂肪酶以及稻谷假单胞菌和嗜热链芽孢杆菌的脂肪酶进行序列比对，确定了几个潜在的钙配体，其中一个通过定点诱变得到了验证。得出的结论是，钙离子对脂肪酶的稳定作用可能是一种比目前所认识到的更为普遍的现象。
