Effects of amino group modification in discoidal apolipoprotein A-I-egg phosphatidylcholine-cholesterol complexes on their reactions with lecithin:cholesterol acyltransferase.
Effects of amino group modification in discoidal apolipoprotein A-I-egg phosphatidylcholine-cholesterol complexes on their reactions with lecithin:cholesterol acyltransferase.
复制标题
盘状载脂蛋白 A-I-蛋磷脂酰胆碱-胆固醇复合物中氨基修饰对其与卵磷脂：胆固醇酰基转移酶反应的影响。
DOI：
10.1021/bi00335a018
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发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
Sweeny,SA
中科院分区：
文献类型：
--
作者：
Jonas,A;Covinsky,KE;Sweeny,SA
伊利诺伊大学厄巴纳-香槟分校医学院生物化学系，厄巴纳，伊利诺伊州61801接收于1984年9月12日摘要：用胆酸钠透析法制备了人载脂蛋白AI-卵磷脂-胆固醇的盘状复合物，和甲醛在硼氢化钠存在下反应。正赖氨酸残基与负或中性基团（柠康酸酐和双乙烯酮，分别）的调制导致，广泛反应的复合物（90%），在结构上的改变和与纯化的人卵磷脂胆固醇酰基转移酶的反应性显着下降。的结构和动力学效应是部分可逆的改性基团的去除或增加离子强度。保留正电荷和引入两个甲基（还原甲基化）的类似程度的修饰（84%）对复合物的结构或反应性没有影响。这些结果，连同在可变复杂的浓度或在可变温度下的kineticdata，表明载脂蛋白AI的特定赖氨酸残基不参与卵磷脂胆固醇酰基转移酶的活化过程，相反，电荷相互作用和结构变化是负责观察到的激活能力下降。在动力学参数方面，固有K* m值和可能的酶-底物颗粒解离常数受到影响，但活化能保持不变后，化学修饰。
Department of Biochemistry, College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 Received September 12, 1984 abstract: Discoidal complexes of human apolipoprotein AI-egg phosphatidylcholine-cholesterol were prepared by the sodium cholate dialysis procedure and were reacted to varying extents with the amino group reagents citraconic anhydride, diketene, and formaldehyde in the presence of sodium borohydride. Mod-ification of positive lysine residues with negative or neutral groups (citraconic anhydride and diketene, respectively) resulted, for extensively reacted complexes (90%), in structural alterations and in a marked decrease in reactivity with purifiedhuman lecithinxholesterol acyltransferase. The structural and kinetic effects were partially reversible by removal of the modifying groups or by increased ionic strength. Similar extents of modification (84%) with retention of positive charge and introduction of two methyl groups (reductive methylation) had no effect on the structure or the reactivity of the complexes. These results, together with kineticdata at variable complex concentrations or at variable temperatures, indicate that specific lysine residues of apolipoprotein AI are not involved in the lecithinxholesterol acyltransferase activation process; instead, charge interactions and structural changes are responsible for the observed decrease in activating capacity. In terms of kinetic parameters, intrinsic K* m values and probably enzyme-substrate particle dissociation constants are affected, but the activation energies remain the same upon chemical modification.