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Evidence for the Presence of CDP‐Ethanolamine: 1,2‐diacyl‐ sn ‐glycerol Ethanolaminephosphotransferase in Rat Central Nervous System Myelin
Author(s) -
Wu PoShun,
Ledeen Robert W.
Publication year - 1980
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1980.tb03705.x
Subject(s) - cerebroside , microsome , myelin , biochemistry , chemistry , ethanolamine , enzyme , glycerol , lactosylceramide , phospholipid , sphingomyelin , chromatography , membrane , biology , central nervous system , endocrinology
: Highly purified rat brain myelin isolated by two different procedures showed appreciable activity for CDP‐ethanolamine: 1,2‐diacyl‐ sn ‐glycerol ethanolaminephosphotransferase (EC 2.7.8.1). Specific activity was close to that of total homogenate and approximately 12–16% that of brain microsomes. Three other lipid‐synthesizing enzymes, cerebroside sulfotransferase, lactosylceramide sialyltransferase, and serine phospholipid exchange enzyme, were found to have less than 0.5% the specific activity in myelin compared with microsomes. Washing the myelin with buffered salt or taurocholate did not remove the phosphotransferase, but activity was lost from both myelin and microsomes by treatment with Triton X‐100. It resembled the microsomal enzyme in having a pH optimum of 8.5 and a requirement for Mn 2+ and detergent, but differed in showing no enhancement with EGTA. The diolein K m was similar for the two membranes (2.5–4 × 10 −4 m ), but the CDP‐ethanolamine K m was lower for myelin (3–4 × 10 −5 m ) than for microsomes (11–13 × 10 −5 m ). Evidence is reviewed that this enzyme is able to utilize substrate from the axon in situ .