Properties and subcellular localization of myocardial fatty acyl-coenzyme A oxidase.
The properties and subcellular localization of fatty acyl-CoA oxidase (FAO) were studied in rat heart homogenates. After differential centrifugation, FAO was sedimentable and enriched in a "light-mitochondrial" fraction. FAO had a pH optimum of 8-9. Among straight-chain, saturated fatty acyl-CoAs, the enzyme showed a marked preference for medium chain substrates (C12 greater than C10 = C8 greater than C16 = C14 greater than C6) over a concentration range up to 100 microM. No activity was observed with C4-CoA. The apparent Michaelis constant (Km) for C12-CoA was 5-10 microM. After removal of nuclei by low-speed centrifugation, combined subcellular particle preparations were obtained by high-speed centrifugation and layered on linear density gradients of metrizamide. After density equilibration, FAO showed a symmetric distribution centered at p = 1.16-1.18, like that of the enzyme catalase, a marker for microperoxisomes. In contrast, enzyme markers for mitochondria, lysosomes, sarcolemma, and sarcoplasmic reticulum were recovered in low-density regions of the gradient. These results provide a direct demonstration of fatty acyl-CoA oxidase in cardiac tissue and its association with microperoxisomes.
Department of Biological Chemistry, School of Medicine, Wright State University, Dayton, Ohio 45435.
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Harrison
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Walusimbi-Kisitu
D042962:Acyl-CoA Oxidase; D000818:Animals; D002458:Cell Fractionation / Q000379:methods; D002499:Centrifugation, Density Gradient / Q000379:methods; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010088:Oxidoreductases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000201:enzymology
D010088:Oxidoreductases; D042962:Acyl-CoA Oxidase