Effect of Fe2+ and Mn2+ on 3-mercaptopicolinate inhibition of cytosolic and mitochondrial phosphoenolpyruvate carboxykinase of five species.
Liver cytosolic or mitochondrial fractions of five species were incubated with 30 micrometer Fe2+ or with 100 micrometer Mn2+ prior to assaying for phosphoenolpyruvate carboxykinase (GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32) acticity in the presence of 3-mercaptopicolinate. Only the cytosolic carboxykinases were activated 3--4-fold by Fe2+ or Mn2+. Fe2+ enhanced the inhibitory potency of 3-mercaptopicolinate 10--50-fold against the cytosolic and the mitochondrial carboxykinases, but Mn2+ was ineffective. Mn2+ interfered with Fe2+ -enhancement of inhibition by 3-mercaptopicolinate in a manner competitive with Fe2+. It is hypothesized that Fe2+ and 3-mercaptopicolinate form a coordination complex that inhibits the carboxylkinases and that 3-mercaptopicolinate does not blind to a carboxykinase containing Mn2+.
D000818:Animals; D002417:Cattle; D002645:Chickens; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D005296:Ferrous Compounds / Q000494:pharmacology*; D006168:Guinea Pigs; D007501:Iron / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D008345:Manganese / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000201:enzymology; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000037:antagonists & inhibitors*; D010848:Picolinic Acids / Q000494:pharmacology*; D051381:Rats; D013045:Species Specificity; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013552:Swine
D005296:Ferrous Compounds; D010848:Picolinic Acids; D013438:Sulfhydryl Compounds; D008345:Manganese; C008363:3-mercaptopicolinic acid; D007501:Iron; D010729:Phosphoenolpyruvate Carboxykinase (GTP)