4-hydroxybenzoate prenyltransferases in cell-free extracts of Lithospermum erythrorhizon cell cultures

Aromatic prenylation reactions of 4-hydroxybenzoate (4HB) are involved in the biosynthesis of ubiquinones and of shikonin, a naphthoquinone pigment derived from 4HB and geranyldiphosphate (GPP) in Lithospermum erythrorhizon. The enzymic prenylation of 4HB with GPP and with solanesyldiphosphate (SPP) was measured in cell-free extracts from L. erythrorhizon cell cultures. The conversion of GPP was induced by methyl jasmonate, an inducer of shikonin biosynthesis, whilst the conversion of SPP was not, suggesting that the two reactions are carried out by different enzymes. Either reaction was found both in the microsomal fraction and in the organellar membrane fraction. The activity of the 4HB geranyltransferase in the microsomal fraction could be separated from the 4HB solanesyltransferase by partial purification using DEAE Sephacel and Heparin Sepharose affinity columns. The results indicate the presence of two distinct enzymes, GPP:4-HB geranyltransferase and SPP:4-HB solanesyltransferase. The enzymes are apparently quite specific for the chain length of the isoprenoid precursors, which is in contrast to the broad substrate specificity of the polyprenyldiphosphate :4-HB polyprenyltransferase from Escherichia coli. Copyright (C) 1997 Elsevier Science Ltd