HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kimmich, G. A. Articles by Rasmussen, H. Search for Related Content PubMed PubMed Citation Articles by Kimmich, G. A. Articles by Rasmussen, H. Social Bookmarking                      What's this?

Regulation of Pyruvate Carboxylase Activity by Calcium in Intact Rat Liver Mitochondria

From the ¹ From the Department of Biochemistry, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104

Low concentrations of calcium (<100µm) cause a marked inhibition of ¹⁴C-carbon dioxide production from carboxyl-labeled pyruvate by isolated rat liver mitochondria. This effect disappears in the presence of agents which preclude pyruvate carboxylase activity such as dinitrophenol plus oligomycin. Adding ATP in combination with these agents restores carboxylase activity and the inhibitory effect of calcium returns. If malate is added, the system again becomes less dependent on pyruvate carboxylase activity and calcium loses its effectiveness. Malate can also overcome inhibition caused by dinitrophenol.

Pyruvate carboxylase activity can be monitored more directly by measuring the net accumulation of Krebs cycle intermediates formed from pyruvate or incorporation of pyruvate-carboxyl-¹⁴C to the cycle intermediates. Calcium (100µm) inhibited both of these processes by as much as 75%. Studies with partially purified carboxylase confirm the concept that calcium is an effective inhibitor, and indicate that the effect may be due to competition with magnesium ion.

Mitochondria from vitamin D-deficient or cortisone-treated animals exhibited higher carboxylase activities than those of control animals as measured by the indirect ¹⁴CO₂ assay method. These changes are consistent with the known effects of those agents on calcium metabolism in vivo. Results are discussed in terms of the possibility that calcium may play an important role in regulating the initial steps of gluconeogenesis.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?