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The most important biological function of carnitine acyltransferases is the transport of fatty acids for β-oxidation(2).Fatty acids are oxidized for energy production in the mitochondrial matrix by a process called β- oxidation. The major site of fatty acid accumulation, however, is the cytoplasm of the cells. Hence, in order to provide energy, fatty acids have to be transported from the cytoplasm across the inner mitochondrial membrane into the mitochondrial matrix. The carnitine shuttle , a transport chain that consists of three enzymatic reactions, helps fatty acids to pass the mitochondrial membrane. Carnitine acyltransferases (CrATs, CrOTs, CPTs) are part of the carnitine shuttle. | The most important biological function of carnitine acyltransferases is the transport of fatty acids for β-oxidation(2).Fatty acids are oxidized for energy production in the mitochondrial matrix by a process called β- oxidation. The major site of fatty acid accumulation, however, is the cytoplasm of the cells. Hence, in order to provide energy, fatty acids have to be transported from the cytoplasm across the inner mitochondrial membrane into the mitochondrial matrix. The carnitine shuttle , a transport chain that consists of three enzymatic reactions, helps fatty acids to pass the mitochondrial membrane. Carnitine acyltransferases (CrATs, CrOTs, CPTs) are part of the carnitine shuttle. | ||
[[Image:Second step carnitine shuttle.jpg|thumb|second step of the carnitine shuttle|600px|left]] | [[Image:Second step carnitine shuttle.jpg|thumb|second step of the carnitine shuttle|600px|left]] | ||
The first step of the carnitine shuttle is the activation of fatty acids. They are transformed into the activated form (= acyl CoA) by the formation of a thioester linkage between the fatty acid carboxyl group and the thiol group of coenzyme A. The '''second step''' of the carnitine shuttle is catalyzed by <font color='#802828'>'''carnitine acyltransferases'''</font>. These enzymes (especially CPT) facilitate the transport of fatty acids by conjugating them to <font color='#267DAB'>'''carnitine'''</font>. In this reaction an <font color='#c88033'>'''acyl group'''</font> is transferred from the sulfur atom of <font color='#00007C'>'''CoA'''</font> to the hydroxyl group of carnitine. The product is <font color='#c88033'>'''acyl-'''</font> <font color='#267DAB'>'''carnitine'''</font>. The third step of the carnitine shuttle is also catalyzed by <font color='#802828'>'''carnitine acyltransferases'''</font> (especially CPT) in the mitochondrial matrix. In this reaction the <font color='#c88033'>'''acyl group'''</font> of <font color='#c88033'>'''acyl-'''</font> <font color='#267DAB'>'''carnitine'''</font> ester is transferred back to <font color='#00007C'>'''CoA'''</font> to form <font color='#c88033'>'''acyl-'''</font> <font color='#00007C'>'''CoA'''</font>. <ref> Lehninger Principles of Biochemistry ISBN-10: 071677108X | ISBN-13: 978-0716771081 | Publication Date: February 1, 2008 | Edition: 5th </ref> | The first step of the carnitine shuttle is the activation of fatty acids. They are transformed into the activated form (= acyl CoA) by the formation of a thioester linkage between the fatty acid carboxyl group and the thiol group of coenzyme A. The '''second step''' of the carnitine shuttle is catalyzed by <font color='#802828'>'''carnitine acyltransferases'''</font>. These enzymes (especially CPT) facilitate the transport of fatty acids by conjugating them to <font color='#267DAB'>'''carnitine'''</font>. In this reaction an <font color='#c88033'>'''acyl group'''</font> is transferred from the sulfur atom of <font color='#00007C'>'''CoA'''</font> to the hydroxyl group of carnitine. The product is <font color='#c88033'>'''acyl-'''</font> <font color='#267DAB'>'''carnitine'''</font>. The third step of the carnitine shuttle is also catalyzed by <font color='#802828'>'''carnitine acyltransferases'''</font> (especially CPT) in the mitochondrial matrix. In this reaction the <font color='#c88033'>'''acyl group'''</font> of <font color='#c88033'>'''acyl-'''</font> <font color='#267DAB'>'''carnitine'''</font> ester is transferred back to <font color='#00007C'>'''CoA'''</font> to form <font color='#c88033'>'''acyl-'''</font> <font color='#00007C'>'''CoA'''</font>. <ref> Lehninger Principles of Biochemistry |ISBN-10: 071677108X | ISBN-13: 978-0716771081 | Publication Date: February 1, 2008 | Edition: 5th </ref> | ||
== Structure of Carnitine acetyltransferase == | == Structure of Carnitine acetyltransferase == | ||