tailieunhanh - Báo cáo khóa học: Membrane transport of fatty acylcarnitine and free L-carnitine by rat liver microsomes

Recent studies have suggested that parts of the hepatic activities of diacylglycerol acyltransferase and acyl choles-terol acyltransferase are expressed in the lumen of the endoplasmic reticulum (ER). However the ER membrane is impermeable to the long-chain fatty acyl-CoA substrates of these enzymes. Livermicrosomal vesicles thatwere shown to be at least 95%impermeable topalmitoyl-CoAwere used to demonstrate the membrane transport of palmitoylcarnitine and freeL-carnitine – processes that are necessary for an indirect route of provision of ER luminal fatty acyl-CoA through a luminal carnitine acyltransferase (CAT). . | Eur. J. Biochem. 271 954-961 2004 FEBS 2004 doi Membrane transport of fatty acylcarnitine and free L-carnitine by rat liver microsomes Jason M. Gooding Majid Shayeghi and E. David Saggerson Department of Biochemistry and Molecular Biology University College London UK Recent studies have suggested that parts of the hepatic activities of diacylglycerol acyltransferase and acyl cholesterol acyltransferase are expressed in the lumen of the endoplasmic reticulum ER . However the ER membrane is impermeable to the long-chain fatty acyl-CoA substrates of these enzymes. Liver microsomal vesicles that were shown to be at least 95 impermeable to palmitoyl-CoA were used to demonstrate the membrane transport of palmitoylcarnitine and free L-carnitine - processes that are necessary for an indirect route of provision of ER luminal fatty acyl-CoA through a luminal carnitine acyltransferase CAT . Experimental conditions and precautions were established to permit measurement of the transport of 14C palmitoylcarnitine into microsomes through the use of the luminal CAT and acyl-CoA ethanol acyltransferase as a reporter system to detect formation of luminal 14C palmitoyl-CoA. Rapid unidirectional transport of free L- 3H carnitine by microsomes was measured directly. This process mediated either by a channel or a carrier was inhibited by mersalyl but not by N-ethylmaleimide or sulfobetaine - properties that differentiate it from the mitochondrial inner membrane carnitine acylcarnitine exchange carrier. These findings are relevant to the understanding of processes for the reassembly of triacylglycerols that lipidate very low density lipoprotein particles as part of a hepatic triacylglycerol lipolysis re-esterification cycle. Keywords acylcarnitine carnitine microsomes liver transport. Although mammalian intracellular membranes are impermeable to the Coenzyme A thioesters of long-chain fatty acids these activated derivatives which are synthesized from .