Physiological state and the sensitivity of liver mitochondrial outer membrane carnitine palmitoyltransferase to malonyl-CoA. Correlations with assay temperature, salt concentration and membrane lipid composition. |
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Authors: | I Ghadiminejad D Saggerson |
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Institution: | Department of Biochemistry and Molecular Biology, University College London, U.K. |
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Abstract: | 1. Liver mitochondrial outer membranes were pre-exposed to media of low (20 mM phosphate) or high salt concentration (20 mM phosphate + 0.3 M KCl) before assay of carnitine palmitoyltransferase (CPT) at 25 degrees C. 2. With membranes from fed rats, exposure to high salt decreased sensitivity of CPT to malonyl-CoA whereas high salt increased sensitivity of CPT to malonyl-CoA in membranes from 48 hr-fasted rats. These changes were paralleled by alterations in the KD for high affinity binding of 14C]malonyl-CoA to outer membranes. 3. Decreasing the CPT assay temperatures from 25 to 10 degrees C caused qualitatively similar changes to those seen on exposure to high salt. 4. The relative content of sphingomyelin was increased 2-fold and 4-fold in liver mitochondrial outer membranes from fasted and diabetic rats respectively. Fasting had no effect on the content of cholesterol whereas diabetes decreased this by a third. |
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