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.
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.
Ghadiminejad
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I
Department of Biochemistry and Molecular Biology, University College London, U.K.
Saggerson
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D
D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000502:physiology; D005215:Fasting / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology*; D008316:Malonyl Coenzyme A / Q000502:physiology*; D008563:Membrane Lipids / Q000302:isolation & purification / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology*; D010710:Phosphates / Q000378:metabolism; D011189:Potassium Chloride / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature
D008563:Membrane Lipids; D010710:Phosphates; D008316:Malonyl Coenzyme A; D011189:Potassium Chloride; D002334:Carnitine O-Palmitoyltransferase