Characterization of the in vitro conversion of dolichol to dolichoate in bovine thyroid.
The enzymic conversion of dolichol into dolichoic acid has been studied in bovine thyroid subcellular fractions using [1-3H]dolichol as a substrate. The presence of conversion activity could be demonstrated in both the mitochondrial- and supernatant fractions. Investigation of cofactor requirements revealed that NAD+ was essential for reaching optimal activity. From kinetic studies Km-values of 3.5-4 microM and 0.29 mM could be calculated for, respectively, dolichol and NAD+ using the mitochondrial fraction as an enzyme source. No inhibitory effects from ethanol or pyrazole were detected suggesting that alcohol dehydrogenase is not involved in the dolichol-->dolichoate conversion as observed in a bovine thyroid mitochondrial fraction. From inhibitor studies the conversion system behaves distinctly differently from the NADP(+)-depending microsomal oxidoreductase as well as from catalase. The conversion activity in the supernatant on the other hand must be ascribed, at least partially, to a side activity of alcohol dehydrogenase.
Van Dessel
G
G
UIA Laboratory for Pathological Biochemistry, Department of Medicine, University of Antwerp, Wilrijk, Belgium.
Lagrou
A
A
Hilderson
H J
HJ
Dierick
W
W
D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors; D000818:Animals; D002250:Carbon Radioisotopes; D002264:Carboxylic Acids / Q000737:chemistry*; D002417:Cattle; D003505:Cyclodextrins / Q000494:pharmacology; D004286:Dolichols / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism; D013729:Terpenes / Q000737:chemistry*; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium; D047392:beta-Cyclodextrins
D002250:Carbon Radioisotopes; D002264:Carboxylic Acids; D003505:Cyclodextrins; D004286:Dolichols; D004791:Enzyme Inhibitors; D013729:Terpenes; D047392:beta-Cyclodextrins; D014316:Tritium; D012710:Serum Albumin, Bovine; D000426:Alcohol Dehydrogenase; C031215:betadex