清华大学生物化学脂肪分解代谢.pptxVIP

Chapter 17 Fatty Acid Catabolism;1. The good and bad sides of using triacylglycerols as an energy storage ; ;2. Dietary triacylglycerols are emulsified and absorbed by the intestine;Processing of dietary lipids in vertebrates;Processing of dietary lipids in vertebrates ;Molecular structure of a chylomicron;Molecular structure of a chylomicron ; ;3. Mobilization of stored triacylglycerols in adipocytes needs hormone to signal the demand;Mobilization of triacylglycerols stored in adipose tissue;Entry of glycerol into the glycolytic pathway;4. Early labeling experiments (1904): fatty acids are degraded by sequential removal of two-carbon units;Franz Knoop’s labeling experiments (1904): fatty acids are degraded by oxidation at the b carbon, i.e., b oxidation ;5. Fatty acid oxidation was found to occur in mitochondria ;6. Fatty acids are activated on the outer membrane of mitochondria;Conversion of a fatty acid to a fatty acyl-CoA;7. Activated (long chain) fatty acids are carried into the matrix by carnitine;Fatty acid entry into mitochondria via the acyl-carnitine/carnitine transporter; ;8. Fatty acyl-CoA is oxidized to acetyl-CoA via multiple rounds of b oxidation ;The b-oxidation pathway; ; The hydration step, stereospecifically catalyzed by enoyl-CoA hydratase, converts the trans-?2-enoyl-CoA to L-b-hydroxylacyl-CoA (the cis isomer can also be converted, but to the D isomer). ; The 2nd dehydrogenation is catalyzed by L-b-hydroxylacyl-CoA dehydrogenase, converting L-b-hydroxylacyl-CoA to b-ketoacyl-CoA (not act on the D isomer), with electrons collected by NAD+. ; ;A conserved reaction sequence to induce a carbonyl function on the carbon b to a carboxyl group;Stages of fatty acid oxidation;Palmitol-CoA + 7CoA + 7FAD + 7NAD+ + 7H2O 8 acetyl-CoA + 7FADH2 + 7NADH + 7H+ ;;Hibernating grizzly bears use body fat as their sole fuel;9. Oxidation of unsaturated fatty acids requires one or two auxiliary enzymes, an isomerase and a reductase