On the biosynthesis of ubiquinones in plant mitochondria

Isolated mitochondria from potato tubers, spinach leaves, and daffodil petals from intermediates of the ubiquinone biosynthetic pathway (prenylated 4-hydroxybenzoate, prenylated phenols, and quinoid compounds) from [1-14C]isopentenyl diphosphate and endogenous or exogenous 4-hydroxybenzoate. In contrast [2-14C]mevalonate 5-diphosphate, the immediate precursor of isopentenyl diphosphate was not accepted as a substrate. These results suggest that plant mitochondria have their own prenyltransferase and prenylation system, similar to the plastid compartment which also starts by the use of isopentenyl diphosphate [see Kreuz, K. and Kleinig, H. (1984) Eur. J. Biochem. 141, 531-535].