Phosphatidylcholine Synthesis in Castor Bean Endosperm 1
AUTOR(ES)
Moore, Thomas S.
RESUMO
Three pathways for phosphatidylcholine synthesis were assayed in castor bean (Ricinus communis var. Hale) endosperm. Phosphatidylethanolamine: S-adenosylmethionine methyl transferase occurred predominantly in the endoplasmic reticulum fraction, but some activity appeared in the mitochondria. Phosphorylcholine glyceride transferase occurred exclusively in the endoplasmic reticulum. The phosphorylcholine glyceride transferase activity was approximately 20-fold greater than the methylation pathway in the endoplasmic reticulum. No exchange activity was found. The Michaelis constant for the methylation was 31 μm for S-adenosylmethionine; phosphatidylethanolamine promoted the reaction slightly while other intermediates stimulated it by about 50%. The pH optimum was 9. Phosphorylcholine glyceride transferase had a Michaelis constant of 9.7 μm for cytidine diphosphate choline but variable results were obtained from diglycerides. The pH optimum was 7.5 and a divalent cation was required, Mg2+ giving the greatest stimulation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=542030Documentos Relacionados
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