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Yeast acetyl-CoA carboxylase: In vitro phosphorylation by mammalian and yeast protein kinases

1990; Elsevier BV; Volume: 169; Issue: 2 Linguagem: Inglês

10.1016/0006-291x(90)90341-j

1090-2104

Lee A. Witters, Thomas D. Watts,

Fermentation and Sensory Analysis

Acetyl-CoA carboxylase (ACC) is regulated in mammalian tissues, in part, by multisite enzyme phosphorylation. Yeast ACC (Y-ACC) has been highly purified from S. cerevisiae by monomeric avidin-Sepharose chromatography, revealing an enzyme subunit species of molecular mass 265,000 Da. Unlike mammalian enzyme, Y-ACC is citrate-independent, and reacts weakly or not at all with a panel of anti- rat liver ACC antibodies Like rat ACC, Y-ACC is rapidly phosphorylated and inactivated by two mammalian carboxylase kinases, the cAMP-dependent protein kinase and 5′-AMP-stimulated kinase. It is also phosphorylated by rat liver casein kinase II, but without any change in catalytic activity. Three major yeast protein kinases active on ACC have been fractionated; all co-elute with kinases active on casein, but each appears to be a distinct catalytic species. Like the mammalian casein kinases, however, phosphorylation of ACC by these yeast kinases does not alter yeast ACC activity. Taken together, these data indicate that Y-ACC possesses at least two classes of phosphorylation sites, one or more of which acutely regulates enzyme activity. Alterations in Y-ACC phosphorylation in yeast, as in mammalian tissues, could be an important modulator of the rates of fatty acid synthesis.