Biosynthesis of the side chain of ubiquinone:trans-prenyltransferase in rat liver microsomes.
The trans-prenyltransferase activity present in rat liver microsomes was investigated using an in vitro system. Geranyl-PP, but not farnesyl-PP is utilized as substrate. The pH optimum is at 8.0, and Mn2+ and Mg2+ activate, while Zn2+ completely inhibits the enzyme. Digitonin, taurodeoxycholate, and Tween 80 increase this activity, whereas deoxycholate and SDS are inhibitory. In contrast to the cis-prenyltransferase, the trans-prenyltransferase is not dependent on cytosolic protein factors. The trans-prenyltransferase is present at the cytoplasmic surface of rough and smooth microsomes. Solanesyl-PP and all-trans-geranylgeranyl-PP inhibit the transferase activity but poly-cis-polyprenyl-12-PP, an intermediate in the cis-prenyltransferase reaction, does not. The enzyme reaction gives rise to two products, solanesyl-PP and an unidentified polyprenyl metabolite. Mevinolin treatment distinguishes this enzyme from the cytoplasmic geranylgeranyl-PP synthase. The results demonstrate that rat liver microsomes synthesize solanesyl-PP via a trans-prenyltransferase, which is distinct from cis-prenyltransferase and geranylgeranyl-PP synthase.
Teclebrhan
H
H
Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden.
Olsson
J
J
Swiezewska
E
E
Dallner
G
G
D000818:Animals; D002413:Cations, Divalent; D002451:Cell Compartmentation; D004122:Dimethylallyltranstransferase / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D008148:Lovastatin / Q000494:pharmacology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity; D014451:Ubiquinone / Q000096:biosynthesis*
D002413:Cations, Divalent; D014451:Ubiquinone; D008148:Lovastatin; D004122:Dimethylallyltranstransferase; D010450:Endopeptidases