Re evaluation of the kinetic mechanism of the choline acetyltransferase reaction

L. B. Hersh, M. Peet

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Initial velocity patterns for human placental choline acetyltransferase show a series of converging lines for both the forward and reverse reaction; with K(acetyl coenzyme A)=11.9μM, K(choline)=0.41mM, K(CoA)=8.8μM, and K(acetylcholine)=1.3mM. The relative rates of acetylcholine synthesis (V(f)) to acetylcholine breakdown (V(r)) is 4.5. Product inhibition by acetylcholine is competitive with respect to choline and noncompetitive with respect to acetyl-CoA, while product inhibition by choline is competitive with respect to acetylcholine and noncompetitive with respect to coenzyme A. Chlorocholine, diethylaminoethanol, and acetylaminocholine were used as dead-end inhibitors and shown to inhibit competitively with respect to choline, acetyl-CoA, and CoA. At high choline concentrations, uncompetitive substrate inhibition is observed, and inhibition by acetylaminocholine changes from noncompetitive to competitive. Comparing the reactivity of dimethylaminoethanol to choline, and acetyldimethylaminoethanol to acetylcholine, the maximal velocities obtained with these analogues was ∞25% of the natural substrates. These data are not consistent with the previously proposed ordered Theorell-Chance reaction mechanism, and have been interpreted in terms of a random binding mechanism.

Original languageEnglish
Pages (from-to)4796-4802
Number of pages7
JournalJournal of Biological Chemistry
Issue number14
StatePublished - 1977

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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