磷脂酸双层对猪心脏AMP脱氨酶的影响。pH依赖性脂质相变的关键作用。
The influence of phosphatidate bilayers on pig heart AMP deaminase. Crucial role of pH-dependent lipid-phase transition.
作者信息
Woźniak M, Kossowska E, Purzycka-Preis J, Zydowo M M
机构信息
Department of Biochemistry, Academic Medical School, Gdańsk, Poland.
出版信息
Biochem J. 1988 Nov 1;255(3):977-81. doi: 10.1042/bj2550977.
Phosphatidate bilayers composed of dilauroylphosphatidate, dimyristoylphosphatidate, dipalmitoylphosphatidate and dioleoylphosphatidate were prepared. Their interaction with AMP deaminase isolated from pig heart was investigated. Dioleoylphosphatidate bilayers were found to exert non-competitive inhibition on the AMP deaminase with a Ki of 15 x 10(-6) M. This inhibition is three orders of magnitude stronger than that exerted by orthophosphate. The phosphatidate species containing saturated fatty acids were either non-inhibitory or inhibited enzyme activity rather poorly. However, alkalinization of the medium from pH 6.5 to pH 7.9 led to the inhibition of pig heart AMP deaminase by dilauroylphosphatidate bilayers. This was accompanied by the fluidization of the saturated phosphatidate species, i.e. the lowering of their phase transition temperature in alkaline pH, as measured by light-scattering and fluorescence scans. The possible significance of these findings for the regulation of AMP deaminase activity in vivo by natural membranes is discussed.
制备了由二月桂酰磷脂酸、二肉豆蔻酰磷脂酸、二棕榈酰磷脂酸和二油酰磷脂酸组成的磷脂酸双层。研究了它们与从猪心分离的AMP脱氨酶的相互作用。发现二油酰磷脂酸双层对AMP脱氨酶具有非竞争性抑制作用，抑制常数Ki为15×10⁻⁶ M。这种抑制作用比正磷酸盐强三个数量级。含有饱和脂肪酸的磷脂酸种类要么无抑制作用，要么对酶活性的抑制作用很差。然而，将培养基的pH从6.5碱化至7.9会导致二月桂酰磷脂酸双层对猪心AMP脱氨酶产生抑制作用。通过光散射和荧光扫描测量发现，这伴随着饱和磷脂酸种类的流动性增加，即在碱性pH下其相变温度降低。讨论了这些发现对于天然膜在体内调节AMP脱氨酶活性的可能意义。
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