On the nature of three forms of phosphoenolpyruvate carboxykinase occurring in the cytosol of chicken liver.
Chicken liver mitochondria contained two forms of phosphoenolpyruvate (PEP) carboxykinase (designated as Mt-I and Mt-II) and the chicken liver cytosol fraction contained three forms of PEP carboxykinase (designated as Sol-I, Sol-II, and Sol-III). Mt-I and Mt-II were purified to homogeneity. They both had a molecular weight of 72,000 as judged by the sodium dodecyl-sulfate-polyacrylamide gel electrophoresis method, whereas an apparent molecular weight of 42,000 was obtained for both enzymes when estimated by Sephadex G-100 gel filtration. Studies with a rabbit antibody against the purified Mt-I revealed that Mt-I, Mt-II, Sol-I, and Sol-II are immunochemically identical, whereas Sol-III is immunochemically different from any of the other proteins. Genetic analogy between Mt-I and Mt-II was also suggested by gel electrophoretic analysis of their peptide maps. The content of Sol-III in the adult chicken liver was very small, whereas the livers of chick embryo and very young chick contained a considerable amount of Sol-III. The level of Sol-III in the adult chicken, however, could be significantly increased by the administration of hydrocortisone or isoproterenol. Apparently Sol-III is a cytosol-specific PEP carboxykinase which is similar to the cytosolic PEP carboxykinases of various mammals. Sol-III showed a molecular weight of about 60,000 as estimated by gel filtration. Studies with combined use of the antibody and [3H]leucine revealed that some portion of PEP carboxykinase (Sol-I plus Sol-II) appearing in the liver cytosol corresponds to a precursor in transit to the mitochondria, although major portions of Sol-I and Sol-II appear to be accounted for by release of the mitochondrial enzymes.
D000818:Animals; D002642:Chick Embryo; D002645:Chickens / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D006854:Hydrocortisone / Q000494:pharmacology; D005779:Immunodiffusion; D007545:Isoproterenol / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000201:enzymology; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000032:analysis* / Q000378:metabolism
D010446:Peptide Fragments; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D007545:Isoproterenol; D006854:Hydrocortisone