Wong H, Davis R C, Nikazy J, Seebart K E, Schotz M C
Lipid Research, Veterans Administration Wadsworth Medical Center, Los Angeles, CA 90073.
Proc Natl Acad Sci U S A. 1991 Dec 15;88(24):11290-4. doi: 10.1073/pnas.88.24.11290.
Hepatic lipase and lipoprotein lipase hydrolyze fatty acids from triacylglycerols and are critical in the metabolism of circulating lipoproteins. The two lipases are similar in size and amino acid sequence but are distinguished by functional differences in substrate preference and cofactor requirement. Presumably, these distinctions result from structural differences in functional domains. To begin localization of these domains, a chimeric lipase was constructed composed of the N-terminal 329 residues of rat hepatic lipase linked to the C-terminal 136 residues of human lipoprotein lipase. The chimera hydrolyzed both monodisperse short-chain (esterase) and emulsified long-chain (lipase) triacylglycerol substrates with catalytic and kinetic properties closely resembling those of native hepatic lipase. However, monoclonal antibodies to lipoprotein lipase inhibited the lipase activity, but not the esterase function, of the chimera. Therefore, the chimeric molecule is a functional lipase and contains elements and characteristics from both parental enzymes. It is proposed that the N-terminal domain, containing the active center from hepatic lipase, governs the catalytic character of the chimera, and the C-terminal domain is essential for hydrolysis of long-chain substrates.
肝脂酶和脂蛋白脂酶可从三酰甘油中水解脂肪酸，在循环脂蛋白的代谢中起关键作用。这两种脂酶在大小和氨基酸序列上相似，但在底物偏好和辅因子需求的功能差异上有所区别。据推测，这些差异源于功能域的结构差异。为了开始定位这些结构域，构建了一种嵌合脂酶，它由大鼠肝脂酶的N端329个残基与人类脂蛋白脂酶的C端136个残基相连组成。该嵌合体可水解单分散短链（酯酶）和乳化长链（脂酶）三酰甘油底物，其催化和动力学特性与天然肝脂酶非常相似。然而，针对脂蛋白脂酶的单克隆抗体抑制了嵌合体的脂酶活性，但不抑制其酯酶功能。因此，嵌合分子是一种功能性脂酶，包含来自两种亲本酶的元件和特征。有人提出，包含肝脂酶活性中心的N端结构域决定了嵌合体的催化特性，而C端结构域对于长链底物的水解至关重要。
