Fatty-Acid ATP synthase

Fatty-Acid ATP synthase - Molecular Biochemistry II Fatty...

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Fatty Acid Oxidation Copyright © 1999-2007 by Joyce J. Diwan. All rights reserved. Molecular Biochemistry II
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A 16-C fatty acid with numbering conventions is shown. Most naturally occurring fatty acids have an even number of carbon atoms. The pathway for catabolism of fatty acids is referred to as the β -oxidation pathway, because oxidation occurs at the β -carbon (C-3). C O O - 1 2 3 4 α β γ fatty acid with a cis- 9 double bond
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Triacylglycerols (triglycerides) are the most abundant dietary lipids. They are the form in which we store reduced C for energy. Each triacylglycerol has a glycerol backbone to which are esterified 3 fatty acids Most triacylglycerols are “ mixed .” The 3 fatty acids differ glycerol fatty acid triacylglycerol H 2 C HC H 2 C OH OH OH H 2 C HC H 2 C O O O C R O C C R O R O HO C R O
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Lipid digestion, absorption, transport will be covered separately. Lipases hydrolyze triacylglycerols, releasing 1 fatty acid at a time, yielding diacylglycerols, & eventually glycerol. glycerol fatty acid triacylglycerol H 2 C HC H 2 C OH OH OH H 2 C HC H 2 C O O O C R O C C R O R O HO C R O
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glycerol glycerol-3-P dihydroxyacetone-P CH 2 CH CH 2 OH HO O PO 3 - CH 2 CH CH 2 OH HO OH CH 2 C CH 2 OH O PO 3 - O ATP ADP H + + NAD + NADH 1 2 Glycerol , arising from hydrolysis of triacylglycerols, is converted to the Glycolysis intermediate dihydroxyacetone phosphate , by reactions catalyzed by: 1 Glycerol Kinase 2 Glycerol Phosphate Dehydrogenase.
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Free fatty acids , which in solution have detergent properties, are transported in the blood bound to albumin , a serum protein produced by the liver. Several proteins have been identified that facilitate transport of long chain fatty acids into cells , including the plasma membrane protein CD36 . C O O - 1 2 3 4 α β γ fatty acid with a cis- 9 double bond
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Fatty acid activation: Fatty acids must be esterified to Coenzyme A before they can undergo oxidative degradation, be utilized for synthesis of complex lipids, or be attached to proteins as lipid anchors. Acyl-CoA Synthases (Thiokinases) of ER & outer mitochondrial membranes catalyze activation of long chain fatty acids, esterifying them to coenzyme A. This process is ATP-dependent , & occurs in 2 steps. There are different Acyl-CoA Synthases for fatty acids of different chain lengths.
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Acyl-CoA Synthases Exergonic PP i (P~P) hydrolysis, catalyzed by Pyrophosphatase, makes the coupled reaction spontaneous. 2 ~P bonds of ATP are cleaved. The acyl-CoA product includes one "~" thioester linkage. Fatty acid activation N N N N NH 2 O OH OH H H H CH 2 H O P O P O P - O O O - O - O O O - N N N N NH 2 O OH OH H H H CH 2 H O P O C O O - R O S C R O CoA R C O O - PP i CoA SH AMP 2 P i fatty acid ATP acyl- adenylate acyl-CoA
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Summary of fatty aid activation: fatty acid + ATP acyladenylate + PP i PP i 2 P i acyladenylate + HS-CoA acyl-CoA + AMP Overall: fatty acid + ATP + HS-CoA acyl-CoA + AMP + 2 P i
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Fatty-Acid ATP synthase - Molecular Biochemistry II Fatty...

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