Kinetic selectivity of cholinephosphotransferase in mouse liver: The K(m) for CDP-choline depends on diacylglycerol structure

C. R. Mantel, A. R. Schulz, K. Miyazawa, H. E. Broxmeyer

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

The effects of different 1,2-diacyl-sn-glycerols on the kinetic properties of CDP-choline: 1,2-diacylglycerol cholinephosphotransferase (EC 2.7.8.2) from mouse liver microsomes have been studied. Initial-velocity experiments were carried out with various concentrations of several species of diacylglycerol at different fixed concentrations of CDP-choline. Kinetic analysis of these data showed a family of intersecting lines consistent with a sequential kinetic mechanism of catalysis. The K(m) and V(max) values derived from rate data revealed a pronounced effect of diacylglycerol species utilization on the K(m) value for CDP-choline. There was a biphasic relationship between diacylglycerol chain length and the K(m) for CDP-choline. Substitution of an unsaturated fatty acid in the sn-2 position of distearin also dramatically increased the CDP-choline K(m) value as well as the V(max); 1,2-Dipalmitoyl-sn-glycerol was the preferred substrate over other disaturated species, but 1,2-dihexanoyl-sn-glycerol could not be utilized. These results demonstrate the kinetic mechanism of in vitro catalysis and suggest a regulatory role for CDP-choline concentration in the diacylglycerol species selectivity of cholinephosphotransferase resulting in the de novo biosynthesis of different molecular species of phosphatidylcholine.

Original languageEnglish (US)
Pages (from-to)815-820
Number of pages6
JournalBiochemical Journal
Volume289
Issue number3
DOIs
StatePublished - 1993

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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