Malonyl-Coenzyme A is a key intermediate in the fatty acid biosynthetic pathway. The cardiac tissue, unlike most other tissues, is not known to synthesize fatty acids. However, high levels of malonyl-CoA (4-5 uM) are found in the heart tissue. This project is an investigation of the pathways of formation and degradation of malonyl-CoA in the heart. It has been proposed that malonyl-CoA may serve as an inhibitor of fatty acid oxidation. Since fatty acid oxidation is the key energy yielding pathway for the cardiac tissue, such a control may be very significant. The synthesis of malonyl-CoA by protein fractions derived from heart tissue will be followed by the incorporation of 14C label from 14C bicarbonate into malonyl-CoA. The degradation of malonyl-CoA will be followed by the appearance of 14C carbon dioxide from [1-14C]malonyl-CoA or the appearance of acetyl-CoA, by a coupled spectrophotometric assay using malate dehydrogenase and citrate synthase. The enzymes involved in the synthesis and degradation will be purified by a combination of classical and affinity purification methods. The effect of hormones like epinephrine and insulin (which have pronounced effects on cardiac energetics) on the phosphorylation state and specific activities of heart acetyl-CoA carboxylase and malonyl-CoA decarboxylase will be studied in heart tissues perfused with these hormones. The concentration of malonyl-CoA and the activities of the above enzymes will also be studied in the ischemic heart. Elucidation of the pathways of malonyl-CoA metabolism and its regulation is imperative for a clearer understanding of cardiac energetics and its regulation. Investigation of the regulation of these enzymes will unravel the mechanism of insulin and epinephrine action on cardiac stimulation and lipolysis. The research will also address the relationship between ischemia induced inhibition of cardiac energy output and increased malonyl-CoA levels.
| Thampy, K G (1989) Formation of malonyl coenzyme A in rat heart. Identification and purification of an isozyme of A carboxylase from rat heart. J Biol Chem 264:17631-4 |
| Thampy, K G; Huang, W Y; Wakil, S J (1988) A rapid purification method for rat liver pyruvate carboxylase and amino acid sequence analyses of NH2-terminal and biotin peptide. Arch Biochem Biophys 266:270-6 |
| Thampy, K G; Wakil, S J (1988) Regulation of acetyl-coenzyme A carboxylase. II. Effect of fasting and refeeding on the activity, phosphate content, and aggregation state of the enzyme. J Biol Chem 263:6454-8 |
| Tansey, F A; Thampy, K G; Cammer, W (1988) Acetyl-CoA carboxylase in rat brain. II. Immunocytochemical localization. Brain Res 471:131-8 |
| Thampy, K G; Wakil, S J (1988) Regulation of acetyl-coenzyme A carboxylase. I. Purification and properties of two forms of acetyl-coenzyme A carboxylase from rat liver. J Biol Chem 263:6447-53 |
