Mori K, Taniguchi S, Kumada K, Nakazawa K, Fujiwara M, Fujiwara M
Thromb Res. 1983 Jan 15;29(2):215-24. doi: 10.1016/0049-3848(83)90143-3.
The enzymatic properties of phospholipid methylation in rabbit platelets were examined using S-adenosyl-L-[methyl-3H]methionine as a substrate. pH optimum for the methylation was around 10.5 under Tris-HCl and glycine-NaOH buffer systems. When Tris-HCl buffer was replaced by phosphate buffer, pH optimum shifted to around 8.0 and the methylation was increased approximately threefold, compared with that in the case of Tris-HCl buffer at pH 8.0. The formation of the 3H-methylated phospholipids was increased by addition of exogenous phosphatidyl-N-monomethylethanolamine or phosphatidyl-N,N-dimethylethanolamine, intermediates of the biosynthesis of phosphatidylcholine from phosphatidylethanolamine. However, the increase in product formations by addition of exogenous intermediates was all but equal under Tris-HCl and phosphate buffer systems at pH 8.0. These results suggest that phosphate ion stimulates the first step of the successive methylation to form phosphatidyl-N-monomethylethanolamine from phosphatidylethanolamine. The methylation in platelets was inhibited to 30% of the basal value with Ca2+ (0.2 mM). However, Ca2+ showed different effects on the methylation in various tissues (activation to 150% of the basal value in the adrenal gland and slight inhibition to 82-88% of corresponding basal values in the liver, lung, kidney and brain).
以S-腺苷-L-[甲基-³H]甲硫氨酸为底物，检测了兔血小板中磷脂甲基化的酶学性质。在Tris-HCl和甘氨酸-NaOH缓冲体系下，甲基化的最适pH约为10.5。当用磷酸盐缓冲液代替Tris-HCl缓冲液时，最适pH移至约8.0，且与pH 8.0的Tris-HCl缓冲液相比，甲基化增加了约三倍。添加外源性磷脂酰-N-单甲基乙醇胺或磷脂酰-N,N-二甲基乙醇胺（由磷脂酰乙醇胺生物合成磷脂酰胆碱的中间体）可增加³H-甲基化磷脂的形成。然而，在pH 8.0的Tris-HCl和磷酸盐缓冲体系下，添加外源性中间体导致的产物形成增加几乎相同。这些结果表明，磷酸根离子刺激了从磷脂酰乙醇胺连续甲基化形成磷脂酰-N-单甲基乙醇胺的第一步。Ca²⁺（0.2 mM）可将血小板中的甲基化抑制至基础值的30%。然而，Ca²⁺对不同组织中的甲基化表现出不同的影响（肾上腺中激活至基础值的150%，肝脏、肺、肾脏和大脑中轻微抑制至相应基础值的82 - 88%）。
