Wolf R A
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Am J Physiol. 1989 Nov;257(5 Pt 1):C926-35. doi: 10.1152/ajpcell.1989.257.5.C926.
Phosphatidylinositol-specific phospholipase C was characterized in the soluble phase and in membrane fractions prepared from rabbit myocardium. Four subforms of soluble phospholipase C were identified and characterized. Activity of one subform was inhibited 80% when cardiolipin was present in substrate vesicles, whereas three subforms were stimulated 2- to 10-fold by cardiolipin. A cationic subform, molecular mass 67 kDa, was stimulated threefold when cardiolipin comprised 2% of the total phospholipid and fivefold when it comprised 12%. The major mechanism for the cardiolipin effect was a decrease in the apparent Michaelis constant (Km) of this subform for substrate. Competition experiments were consistent with binding of this subform to cardiolipin. Phospholipase C activity was present in mitochondrial, microsomal, and sarcolemmal membrane fractions that were essentially free of contamination by cytosol. Detection of membrane-associated phospholipase C was facilitated by cardiolipin. Thus rabbit myocardium contains multiple subforms of soluble phospholipase C that differ substantially in surface charge, molecular mass, and sensitivity to cardiolipin. Anionic phospholipids may be important determinants of intracellular distribution of phospholipase C in myocardial tissue.
在兔心肌制备的可溶性部分和膜部分中对磷脂酰肌醇特异性磷脂酶C进行了表征。鉴定并表征了可溶性磷脂酶C的四种亚型。当底物囊泡中存在心磷脂时，一种亚型的活性被抑制80%，而三种亚型被心磷脂刺激2至10倍。一种分子量为67 kDa的阳离子亚型，当心磷脂占总磷脂的2%时被刺激3倍，占12%时被刺激5倍。心磷脂作用的主要机制是该亚型对底物的表观米氏常数（Km）降低。竞争实验与该亚型与心磷脂的结合一致。磷脂酶C活性存在于线粒体、微粒体和肌膜膜部分中，这些部分基本没有被胞质溶胶污染。心磷脂有助于检测膜相关磷脂酶C。因此，兔心肌含有多种可溶性磷脂酶C亚型，它们在表面电荷、分子量和对心磷脂的敏感性方面有很大差异。阴离子磷脂可能是心肌组织中磷脂酶C细胞内分布的重要决定因素。
