METABOLISM OF PHOSPHOINOSITIDES IN GUINEA-PIG BRAIN SYNAPTOSOMES

Abstract— The subcellular distribution of a number of enzymes concerned with inositol lipid metabolism has been studied in sub‐fractions of disrupted guinea‐pig brain synaptosomes. The enzymes were CDP‐diglyceride: inositol phosphatidate transferase, phospha‐tidylinositol kinase, diphosphoinositide kinase, diphosphoinositide phosphomonoesterase and diphosphoinositide diesterase. The distribution of phosphatidylinositol kinase in sub‐fractions from water‐treated synaptosomes was compared with that of other plasma membrane enzymes. After partial solubilization of synaptosomes by Triton X‐100 the activities of phosphatidylinositol kinase and several other enzymes were examined. Distribution of phosphatidylinositol kinase closely resembled that of acetylcholinesterase in sub‐fractions of synaptosomes. Both enzymes appeared to be localised in the outer membrane of the synaptosome. CDP‐diglyceride: inositol phosphatidate transferase was present in all types of synaptosomal membrane. All three enzymes concerned with diphosphoinositide metabolism were found in the cytoplasm of the synaptosome. Copyright © 1969, Wiley Blackwell. All rights reserved