Purification and partial characterization of acetyl-coA synthetase in rat liver mitochondria.

Acetyl-CoA synthetase (AceCS), which catalyzes the activation of acetate to produce acetyl-CoA, was found to have a much greater Km value for acetate in liver mitochondria than that in the heart mitochondria of rats, indicating that two different types of AceCS are located in the liver and heart mitochodria. Recently, Fujino et al. reported that mouse heart mitochondrial AceCS, designated AceCS2, was expressed in a wide range of tissues, however, it was apparently absent from the liver. In this study, liver mitochondrial AceCS activity, but not heart AceCS2, was greatly induced in di(2-ethylhexyl)phthalate (DEHP)-treated rats. We purified and characterized the rat liver mitochondrial AceCS. The molecular mass of the enzyme estimated by SDS-PAGE was -58 kDa, which was quite different from that of the heart mitochondrial enzyme, AceCS2. The calculated Km value for the acetate of the partially purified liver enzyme was much greater, being about 100 times that of heart enzyme, AceCS2.

Prodigiosin 25-C perturbs permeation of acetate in a cultured cell line.

Prodigiosin 25-C had little effect on DNA, RNA, and protein synthesis, and cellular ATP content, but the drug markedly inhibited the incorporation of acetate into lipid fractions. Under the same conditions, the incorporation of other lipid precursors including glycerol, mevalonate, palmitate, and oleate was not affected. A decrease in the incorporation of acetate was not due to the inhibition of fatty acid biosynthesis, because prodigiosin 25-C did not affect the activity of acetyl-CoA synthetase, acetyl-CoA carboxylase or fatty acid synthase in cell-free assay systems prepared from rat liver cytosol. In contrast, prodigiosin 25-C strongly inhibited the rapid uptake of acetate into acid-soluble fraction in intact cells. The results suggest that prodigiosin 25-C specifically perturbs the permeation of acetate through plasma membranes.