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  • Title: Enzymatic properties of phospholipid methylation in rabbit platelets.
    Author: Mori K, Taniguchi S, Kumada K, Nakazawa K, Fujiwara M, Fujiwara M.
    Journal: Thromb Res; 1983 Jan 15; 29(2):215-24. PubMed ID: 6845277.
    Abstract:
    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).
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