Kinney A J, Carman G M
Department of Food Science, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick 08903.
Proc Natl Acad Sci U S A. 1988 Nov;85(21):7962-6. doi: 10.1073/pnas.85.21.7962.
Evidence is presented that demonstrates that phosphatidylserine synthase (CDPdiacylglycerol:L-serine O-phosphatidyltransferase, EC 2.7.8.8) from Saccharomyces cerevisiae is phosphorylated in vivo and in vitro by cAMP-dependent protein kinase. Phosphatidylserine synthase activity in cell extracts was reduced in the bcy1 mutant (which has high cAMP-dependent protein kinase activity) and elevated in the cyr1 mutant (which has low cAMP-dependent protein kinase activity) when compared with wild-type cells. The reduced phosphatidylserine synthase activity in the bcy1 mutant correlated with elevated levels of a phosphorylated form of the phosphatidylserine synthase Mr 23,000 subunit. The elevated phosphatidylserine synthase activity in the cyr1 mutant correlated with reduced levels of the phosphorylated form of the enzyme. There was negligible phosphorylation of the phosphatidylserine synthase Mr 23,000 subunit from stationary-phase cells. Pure phosphatidylserine synthase was phosphorylated by the cAMP-dependent protein kinase catalytic subunit, which resulted in a 60-70% reduction in phosphatidylserine synthase activity. The cAMP-dependent protein kinase catalytic subunit catalyzed the incorporation of 0.7 mol of phosphate per mol of phosphatidylserine synthase Mr 23,000 subunit. The specific cAMP-dependent protein kinase inhibitor prevented the phosphorylation of phosphatidylserine synthase and the inhibition of its activity by the catalytic subunit. Analysis of peptides derived from protease-treated labeled phosphatidylserine synthase showed only one labeled peptide. Phospho amino acid analysis of labeled phosphatidylserine synthase showed that the enzyme was phosphorylated at a serine residue.
有证据表明，来自酿酒酵母的磷脂酰丝氨酸合酶（CDP二酰甘油：L-丝氨酸O-磷脂酰转移酶，EC 2.7.8.8）在体内和体外均被cAMP依赖性蛋白激酶磷酸化。与野生型细胞相比，bcy1突变体（具有高cAMP依赖性蛋白激酶活性）的细胞提取物中磷脂酰丝氨酸合酶活性降低，而cyr1突变体（具有低cAMP依赖性蛋白激酶活性）的细胞提取物中该酶活性升高。bcy1突变体中磷脂酰丝氨酸合酶活性的降低与磷脂酰丝氨酸合酶23,000 Mr亚基的磷酸化形式水平升高相关。cyr1突变体中磷脂酰丝氨酸合酶活性的升高与该酶磷酸化形式水平的降低相关。静止期细胞的磷脂酰丝氨酸合酶23,000 Mr亚基的磷酸化可忽略不计。纯磷脂酰丝氨酸合酶被cAMP依赖性蛋白激酶催化亚基磷酸化，导致磷脂酰丝氨酸合酶活性降低60-70%。cAMP依赖性蛋白激酶催化亚基催化每摩尔磷脂酰丝氨酸合酶23,000 Mr亚基掺入0.7摩尔磷酸盐。特异性cAMP依赖性蛋白激酶抑制剂可阻止磷脂酰丝氨酸合酶的磷酸化及其被催化亚基的活性抑制。对蛋白酶处理的标记磷脂酰丝氨酸合酶衍生的肽段分析仅显示一个标记肽段。对标记磷脂酰丝氨酸合酶的磷酸氨基酸分析表明该酶在一个丝氨酸残基处被磷酸化。
