Chahinian H, Sarda L
Laboratoire de Biochimie et Physico-chimie des Membranes, Faculté St-Jérôme, Université Paul Cézanne, Marseille, France.
Protein Pept Lett. 2009;16(10):1149-61. doi: 10.2174/092986609789071333.
Carboxylesterases (Carboxyl ester hydrolase) include two groups of enzymes, namely non-specific esterases (EC 3.1.1.1) and lipases (EC 3.1.1.3) which have been early differentiated on the basis of their substrate specificity. Esterases hydrolyse solutions of water-soluble short acyl chain esters and are inactive against water-insoluble long chain triacylglycerols which, in turn, are specifically hydrolyzed by lipases. Based on the comparison of the primary structures, three families of sequence-related carboxylesterases, namely the lipoprotein lipase family (L-family), the hormonesensitive lipase family (H-family) and the cholinesterase family (C-family) have been identified. Using solutions and emulsions of vinyl, glyceryl and p-nitrophenyl esters, we have reinvestigated the kinetic properties of some esterases and lipases of the H- and C-families. Results indicate that esterases and lipases, which are both active on soluble esters, can be differentiated by their value of Km. Moreover, esterase, unlike lipases, are inactive against water-insoluble esters as vinyl laurate and trioctanoylglycerol. From the the comparison of structural features of sequence-related esterases and lipases, it appears that lipases, unlike esterases, display a significant difference in the distribution of hydrophobic amino acid residues at vicinity of their active site. This observation supports the hypothesis of the existence in lipases of a particular surface domain that specifically interacts with lipid-water interfaces and contributes to the transfer a single substrate molecule from the organized lipid-water interface (supersubstrate) to the catalytic site of the enzyme.
羧酸酯酶（羧基酯水解酶）包括两类酶，即非特异性酯酶（EC 3.1.1.1）和脂肪酶（EC 3.1.1.3），它们早期是根据底物特异性区分的。酯酶水解水溶性短酰基链酯溶液，对水不溶性长链三酰甘油无活性，而长链三酰甘油则由脂肪酶特异性水解。基于一级结构的比较，已鉴定出三个与序列相关的羧酸酯酶家族，即脂蛋白脂肪酶家族（L家族）、激素敏感脂肪酶家族（H家族）和胆碱酯酶家族（C家族）。我们使用乙烯基、甘油基和对硝基苯基酯的溶液和乳液，重新研究了H家族和C家族的一些酯酶和脂肪酶的动力学特性。结果表明，对可溶性酯均有活性的酯酶和脂肪酶可通过其Km值区分。此外，与脂肪酶不同，酯酶对水不溶性酯如月桂酸乙烯酯和三辛酰甘油无活性。从与序列相关的酯酶和脂肪酶的结构特征比较来看，脂肪酶与酯酶不同，在其活性位点附近疏水氨基酸残基的分布上存在显著差异。这一观察结果支持了脂肪酶中存在一个特定表面结构域的假设，该结构域与脂质-水界面特异性相互作用，并有助于将单个底物分子从有组织的脂质-水界面（超底物）转移到酶的催化位点。
