The goal of this study was to test the relationship between malonyl-CoA concentration and its turnover measured in isolated rat hearts perfused with NaH13CO3. This turnover is a direct measurement of the flux of acetyl-CoA carboxylation in the intact heart. It also reflects the rate of malonyl-CoA decarboxylation, i.e. the only known fate of malonyl-CoA in the heart. Conditions were selected to result in stable malonyl-CoA concentrations ranging from 1.5 to 5 nmol·g wet weight-1. The malonyl-CoA concentration was directly correlated with the turnover of malonyl-CoA, ranging from 0.7 to 4.2 nmol·min-1·g wet weight-1 (slope = 0.98, r2 = 0.94). The Vmax activities of acetyl-CoA carboxylase and of malonyl-CoA decarboxylase exceeded the rate of malonyl-CoA turnover by 2 orders of magnitude and did not correlate with either concentration or turnover of malonyl-CoA. However, conditions of perfusion that increased acetyl-CoA supply resulted in higher turnover and concentration, demonstrating that malonyl-CoA turnover is regulated by the supply of acetyl-CoA. The only condition where the activity of malonyl-CoA decarboxylase regulated malonyl-CoA kinetics was when the enzyme was pharmacologically inhibited, resulting in increased malonyl-CoA concentration and decreased turnover. Our data show that, in the absence of enzyme inhibitors, the rate of acetyl-CoA carboxylation is the main determinant of the malonyl-CoA concentration in the heart.
CITATION STYLE
Reszko, A. E., Kasumov, T., David, F., Thomas, K. R., Jobbins, K. A., Cheng, J. F., … Brunengraber, H. (2004). Regulation of malonyl-CoA concentration and turnover in the normal heart. Journal of Biological Chemistry, 279(33), 34298–34301. https://doi.org/10.1074/jbc.M405488200
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