Although alterations in fatty acid composition of phospholipids in plasma membranes had no effect on activities of plasma membrane ATPases of a self-flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae cells grown in the absence of ethanol(basal enzymes),they significantly affected the susceptibilities of the enzymes to in vivo activation induced by ethanol:the maximal values for the activated enzymes in cells pregrown with 0. 6 mmol/L palmitic, linoleic or linolenic acid respectively were 3.6,1.5 and 1.2-fold higher than their respective basal levels(in cells grown without ethanol),whereas the corresponding value for cells pregrown in the absence of fatty acid was 2.3-fold,with the concentrations of ethanol for the above maximal in vivo activation of enzymes being 7％,6％,6％ and 7％(V/V) respectively.The Km values for ATP,the pH profiles,and the sensitivities to orthovanadate of the basal and the activated plasma membrane ATPases were essentially identical;however,the vmax values of activated enzymes increased significantly.It was found that the characteristics of phospholipid fatty acid composition of plasma membrane leading to the enhanced ethanol tolerance of this strain,were also efficacious to increase the percentage of activation of plasma membrane ATPase per unit of ethanol.These data support a close correlation between the ethanol tolerance of this strain and the sensitivity of its plasma membrane ATPase to the in vivo ethanol-induced activation.%研究揭示细胞膜磷脂脂肪酸组成与质膜ATP酶在酵母菌耐酒精中的一种新颖关系.实验表明,细胞膜磷脂脂肪酸组成特点对生长于未添加酒精条件下的自絮凝颗粒酵母质膜ATP酶活性没有影响,但却明显影响生长于添加酒精(1%～10%,V/V)条件下的菌体质膜ATP酶对酒精激活的敏感性:预培养于添加0.6 mmol/L棕榈酸、亚油酸、或亚麻酸条件下的菌体的质膜ATP酶的最大激活水平分别为各自酶的基态水平(未激活)的3.6、1.5和1.2倍,而对照组(预培养于未添加脂肪酸条件下的菌体)的相应值为2.3倍,酶产生上述最大激活水平时的酒精浓度分别为7%、6%、6%、和7%(V/V).酶激活后米氏常数Km、最适pH和对钒酸钠(质膜ATP酶特异性抑制剂)的敏感性等性质不变,但最大反应速度vmax明显增加.实验表明,细胞膜磷脂脂肪酸组成特点对提高菌体的耐酒精能力越有利,则其质膜ATP酶被酒精激活的幅度越大,说明菌体耐酒精能力的提高与其质膜ATP酶对酒精激活的敏感性的增加密切相关.细胞膜磷脂脂肪酸组成会影响酵母菌质膜ATP酶对酒精激活的敏感性是观察到的新的实验现象.
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