Shidoji Y, Silverman-Jones C S, De Luca L M
Biochem J. 1983 Dec 15;216(3):727-35. doi: 10.1042/bj2160727.
A remarkable and immediate decrease in GDP-mannose:retinyl phosphate mannosyltransferase activity was found on pre-incubation of rat liver postnuclear membranes with phospholipase A2 or phospholipase C. Under the same conditions of pre-incubation (1 min at 37 degrees C) trypsin did not affect the enzyme activity, whereas pre-incubation for 30 min with trypsin and Pronase abolished enzyme activity. The lipid extract of untreated rat liver membranes partially restored enzyme activity after phospholipase treatment. Sphingomyelin was as active as the endogenous lipids. Other phospholipids were less active in the following order: phosphatidylcholine greater than phosphatidylethanolamine greater than phosphatidylinositol = phosphatidylserine. Dolichyl phosphate mannose synthesis was inhibited less (33%) by phospholipase C than was Ret-P-Man synthesis (98.5%) under identical conditions of incubation, which included 0.025% Triton. However, retinyl phosphate mannose synthesis by purified endoplasmic reticulum was found to be resistant to phospholipase C. Mixing experiments failed to demonstrate an inhibitory effect of the phospholipase-treated postnuclear membrane fraction on the synthetic activity of the endoplasmic reticulum, thus excluding the release of an inhibitory factor from the postnuclear membranes.
在将大鼠肝脏核后膜与磷脂酶A2或磷脂酶C预孵育时，发现GDP-甘露糖：视黄基磷酸甘露糖基转移酶活性显著且立即降低。在相同的预孵育条件下（37℃孵育1分钟），胰蛋白酶不影响该酶活性，而用胰蛋白酶和链霉蛋白酶预孵育30分钟则会使酶活性丧失。未处理的大鼠肝脏膜的脂质提取物在磷脂酶处理后部分恢复了酶活性。鞘磷脂与内源性脂质的活性相当。其他磷脂的活性较低，顺序如下：磷脂酰胆碱＞磷脂酰乙醇胺＞磷脂酰肌醇 = 磷脂酰丝氨酸。在相同的孵育条件下（包括0.025% Triton），磷脂酶C对多萜醇磷酸甘露糖合成的抑制作用（33%）比对视黄基磷酸甘露糖合成的抑制作用（98.5%）小。然而，发现纯化的内质网对视黄基磷酸甘露糖合成具有抗磷脂酶C的特性。混合实验未能证明经磷脂酶处理的核后膜部分对内质网合成活性有抑制作用，因此排除了从核后膜释放抑制因子的可能性。
