Abstract
Prenylation plays an important role in the biosynthesis of plant secondary metabolites and quinones, e.g. ubiquinone. Recently, we have isolated two cDNAs of prenyltransferase (LePGT-1 and -2) which prenylates p-hydroxybenzoate (PHB) in the biosynthesis of naphthoquinone, shikonin, from Lithospermum erythrorhizon. Both LePGT showed similar expression pattern in plant and responses to several factors which regulate the shikonin biosynthesis. Both LePGT showed strict substrate specificity for geranyl diphosphate as prenyl donor. A detailed enzymatic characterization of recombinant LePGTs expressed in yeast, however, revealed that these two LePGTs showed apparent different Vmax and the Km values for both prenyl acceptor and donor. To understand the functional differences of two LePGTs, we constructed 5 mutant LePGTs which had a deletion in the conserved region for eukaryotic prenyltransferase. The microsomal fractions of yeast transformants harboring these constructs did not show the enzyme activity. Further characterization of recombinant proteins are in progress.
