Differences between manganese and magnesium ions with regard to fatty acid biosynthesis, acetyl-coenzyme A carboxylase activity and malonyl-coenzyme A decarboxylation.
Fatty acid-biosynthetic activity in rat liver cytosol fractions is much greater when the bivalent cation in the assay system is Mn(2+) than when it is Mg(2+). This difference between bivalent cations can be abolished if the cytosol fractions are preincubated with isocitrate and the bivalent cation for 30min before assay of fatty acid-biosynthetic activity. In a search for the biochemical basis of this phenomenon, the following differences between Mg(2+) and Mn(2+) were established: (1) Mn(2+) promotes acetyl-CoA carboxylase activity of the protomeric form of the enzyme under conditions in which Mg(2+) does not; (2) Mn(2+)+ATP have little inhibitory effect on the polymerization of acetyl-CoA carboxylase whereas Mg(2+)+ATP are markedly inhibitory; (3) under conditions in which utilization of malonyl-CoA in condensation reactions is prevented, the steady-state concentration of malonyl-CoA formed by a cytosol fraction is much greater with Mn(2+) than with Mg(2+). The role that each of these specific differences between Mn(2+) and Mg(2+) might play in causing liver cytosol preparations to have greater fatty acid-biosynthetic activity in the presence of Mn(2+) is discussed.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002247:Carbon Isotopes; D002499:Centrifugation, Density Gradient; D002951:Citrates / Q000378:metabolism; D003065:Coenzyme A / Q000378:metabolism*; D005227:Fatty Acids / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008025:Ligases / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology*; D008314:Malonates / Q000378:metabolism; D008345:Manganese / Q000494:pharmacology*; D051381:Rats
D002247:Carbon Isotopes; D002951:Citrates; D005227:Fatty Acids; D008314:Malonates; D008345:Manganese; D000255:Adenosine Triphosphate; D008025:Ligases; D008274:Magnesium; D003065:Coenzyme A