Carnitine biosynthesis in hepatic peroxisomes. Demonstration of gamma-butyrobetaine hydroxylase activity.
We have investigated whether hepatic peroxisomes are capable of synthesizing carnitine. When purified peroxisomes were incubated with gamma-butyrobetaine, a precursor of carnitine, formation of carnitine was observed. These results indicate that peroxisomes contain gamma-butyrobetaine hydroxylase, the enzyme which catalyzes the final step in the biosynthesis of carnitine. This enzyme was previously believed to be present only in the cytosol. gamma-Butyrobetaine hydroxylase activity in peroxisomes was not due to cytosolic contamination as evaluated by marker enzyme analysis. When proliferation of peroxisomes was induced by clofibrate treatment, gamma-butyrobetaine hydroxylase/mass liver increased by 7.6-fold and the specific activity by 2.5-fold. We conclude that hepatic peroxisomes synthesize carnitine and this synthesis becomes substantial under conditions of peroxisomal proliferation.
Paul
H S
HS
Department of Medicine, University of Pittsburgh, School of Medicine, PA.
Sekas
G
G
Adibi
S A
SA
D000818:Animals; D002331:Carnitine / Q000096:biosynthesis*; D002458:Cell Fractionation; D002994:Clofibrate / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D006868:Hydrolysis; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008830:Microbodies / Q000187:drug effects / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D050563:gamma-Butyrobetaine Dioxygenase
D005227:Fatty Acids; D006899:Mixed Function Oxygenases; D050563:gamma-Butyrobetaine Dioxygenase; D002994:Clofibrate; D002331:Carnitine