Enzymes of Lipid Metabolism
Enzymes of Lipid Metabolism
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脂质代谢酶
DOI：
10.1007/978-1-4615-9071-2
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
L. Freysz
中科院分区：
文献类型：
--
作者：
R. Rynbrandt;S. Gatt;L. Freysz
眼镜蛇毒中的磷脂酶AZ是一种均一的热稳定酶，其单体相对分子质量仅为11000，含有一个组氨酸和一个色氨酸残基。该酶对非离子洗涤剂Triton X-100与混合胶束中的磷脂作用最佳；用-‘-手C-核磁共振研究了该洗涤剂与磷脂在混合胶束中的相互作用。在反应中，酶首先与混合胶体结合，然后在与底物的反应中表现出“表面稀释动力学”。最近的研究表明，各种试剂都能使这种磷脂酶AZ失活，从而使其中一种酶分子中的组氨酸发生修饰。这些结果表明，组氨酸残基是活性所必需的，表现出“半反应性”。这些和其他实验被解释为一个模型，该模型认为单体酶在1ipid-水界面形成不对称的二聚体或更高阶的聚集体。所描述的关于磷脂酶AZ与混合小鼠的相互作用的研究是理解洗涤剂对脂肪酶测定的影响的通用模型系统。
Phospho1ipase AZ from cobra venom (Naja naja naja) is a homogeneous, heat-stah1e enzyme that has a monomer mo1ecu1ar weight of on1y 11,000 and contains one histidine and one tryptophan residue. This enzyme acts optimallyon phospho1ipids contained in mixed mice11es with the nonionic detergent Triton X-100; the interactions of this detergent yith pho1§ho1ipid in the mixed mice11es have been e1ucidated with -'-Hand C-NMR. In reacting, the enzyme first associates with the mixed mice11e and then exhibits "surface dilution kinetics" in its reaction with substrate. Re cent studies show that various reagents comp1ete1y inactivate this phospho1ipase AZ resu1ting in the modification of the histidine in on1y one-ha1f of the enzyme molecules. These resu1ts suggest that the histidine residue, which is essential for activity, exhibits "ha1fsi te reactivity." These and other experiments are interpreted in terms of a model that suggests that the monomeric enzyme forms an asymmetrie dimer or higher order aggregate at the 1ipid-water interface. The studies which are described on the interaction of the phospholipase AZ with mixed mice11es serve as a general model system for understanding detergent effects on the assay of lipid enzymes.