J. Biol. Chem., Vol. 266, Issue 26, 17257-17260, Sep, 1991
Is the p29 protein involved in the rapid regulation of phosphoenolpyruvate carboxykinase (GTP)?
W Hoppner, L Beckert, F Buck and HJ Seitz
Abteilung fur Biochemische Endokrinologie, Universitats-Krankenhaus Eppendorf, Hamburg, Federal Republic of Germany.
It has been postulated that a protein with a molecular mass of 29,000
daltons (p29), which copurifies with hepatic phosphoenolpyruvate (P-
enolpyruvate) carboxykinase, forms a complex with the enzyme and stabilizes
its sensitivity to Mn2+ activation by protecting critical sulfhydryl groups
from oxidation (Brinkworth, R. I., Hanson, R. W., Fullin, F. A., and
Schramm, V. L. (1981) J. Biol. Chem. 256, 10795- 10802). In this paper we
demonstrate that p29 is not only expressed in tissues which contain high
amounts of P-enolpyruvate carboxykinase, such as liver and kidney, but also
in brain and muscle, which have no gluconeogenic function. Furthermore, p29
is expressed in rat liver prenatally, whereas P-enolpyruvate carboxykinase
is induced only after birth. The effect of p29 to protect P-enopyruvate
carboxykinase against aerobic oxidation during in vitro incubation was also
observed for ovalbumin and bovine albumin. Peptide sequencing of the p29
and search in a protein data bank revealed a high homology to the
muscle-specific subunit of human phosphoglycerate mutase (EC 2.7.5.3).
Determination of the enzyme activity confirms the identification of the p29
as the rat liver isoform of phosphoglycerate mutase. Taking all these
findings together, it is concluded that this protein has no specific effect
on P- enolpyruvate carboxykinase.
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