Acetylation of choline and homocholine by membrane-bound choline-O-acetyltransferase in mouse forebrain nerve endings.
The choline analog homocholine is not acetylated in vitro by choline-O-acetyltransferase (ChAT, EC 2.3.1.6), which is solubilized by 100 mM-sodium phosphate buffer washes of a crude vesicular fraction of mouse forebrain. However, both homocholine and choline are acetylated by a form of ChAT which is nonionically associated with a subcellular fraction of mouse forebrain containing membrane-associated organelles and occluded acetylcholine (P4). Acetylation of homocholine by membrane-associated ChAT is saturable. 4-(1-Naphthylvinyl)pyridine (NVP) inhibits the acetylation of both choline (60%) and homocholine (40%) by membrane-associated ChAT but reduces the acetylation of choline alone by soluble ChAT (76%). Choline and homocholine serve as competitive alternative substrates for the same membrane-associated ChAT, whereas homocholine acts only as a competitive inhibitor of choline acetylation by soluble ChAT. Acetylhomocholine competitively inhibits the acetylation of choline by both soluble and membrane-associated ChAT more dramatically than does the natural end product, acetylcholine.
D000107:Acetylation; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002794:Choline / Q000031:analogs & derivatives* / Q000378:metabolism*; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051379:Mice; D009286:Naphthylvinylpyridine / Q000494:pharmacology; D009474:Neurons / Q000201:enzymology*; D013379:Substrate Specificity
C007954:homocholine; D009286:Naphthylvinylpyridine; D002795:Choline O-Acetyltransferase; D002794:Choline