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首页> 外文期刊>Biochemistry >The beta 5' loop of the pancreatic lipase C2-like domain plays a critical role in the lipase-lipid interactions.
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The beta 5' loop of the pancreatic lipase C2-like domain plays a critical role in the lipase-lipid interactions.

机译：胰脂肪酶C2样域的β5'环在脂肪酶与脂质的相互作用中起关键作用。

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摘要

The structural similarities between the C-terminal domain of human pancreatic lipase (C-HPL) and C2 domains suggested a similar function, the interaction with lipids. The catalytic N-terminal domain (N-HPL) and C-HPL were produced as individual proteins, and their partitioning between the water phase and the triglyceride-water interface was assessed using trioctanoin emulsions (TC8). N-HPL did not bind efficiently to TC8 and was inactive. C-HPL did bind to TC8 and to a phospholipid monolayer with a critical surface pressure of penetration similar to that of HPL (15 mN m(-1)). These experiments, performed in the absence of colipase and bile salts, support an absolute requirement of C-HPL for interfacial binding of HPL. To refine our analysis, we determined the contribution to lipid interactions of a hydrophobic loop (beta 5') in C-HPL by investigating a HPL mutant in which beta 5' loop hydrophobicity was increased by introducing the homologous lipoprotein lipase (LPL) beta 5' loop. This mutant (HPL-beta 5'LPL) penetrated into phospholipid monolayers at higher surface pressures than HPL, and its level of binding to TC8 was higher than that of HPL in the presence of serum albumin (BSA), an inhibitory protein that competes with HPL for interfacial adsorption. The beta 5' loop of LPL is therefore tailored for an optimal interaction with the surface of triglyceride-rich lipoproteins (VLDL and chylomicrons) containing phospholipids and apoproteins. These observations support a major contribution of the beta 5' loop in the interaction of LPL and HPL with their respective substrates.
机译：人胰脂肪酶（C-HPL）C末端结构域和C2结构域之间的结构相似性表明相似的功能，即与脂质的相互作用。催化的N末端结构域（N-HPL）和C-HPL作为单独的蛋白质生产，并且使用三辛酸乳剂（TC8）评估了它们在水相和甘油三酸酯-水界面之间的分配。 N-HPL不能有效结合TC8，并且没有活性。 C-HPL确实与TC8和磷脂单层结合，其穿透的临界表面压力类似于HPL（15 mN m（-1））。这些实验在不存在脂酶和胆汁盐的条件下进行，支持了HPL界面结合对C-HPL的绝对要求。为了完善我们的分析，我们通过研究HPL突变体（其中通过引入同源脂蛋白脂酶（LPL）β5增加了β5'环的疏水性）来确定C-HPL中疏水环（β5'）对脂质相互作用的贡献。循环。该突变体（HPL-beta 5'LPL）在高于HPL的表面压力下渗透到磷脂单层中，并且在存在与之竞争的抑制蛋白血清白蛋白（BSA）的情况下，其与TC8的结合水平高于HPL。 HPL用于界面吸附。因此，对LPL的beta 5'环进行了定制，以使其与含有磷脂和载脂蛋白的富含甘油三酸酯的脂蛋白（VLDL和乳糜微粒）的表面发生最佳相互作用。这些观察结果支持β5'环在LPL和HPL与它们各自的底物相互作用中的主要贡献。

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