4-HYDROXYBENZOATE 3-GERANYLTRANSFERASE FROM LITHOSPERMUM-ERYTHRORHIZON - PURIFICATION OF A PLANT MEMBRANE-BOUND PRENYLTRANSFERASE

Geranyldiphosphate:4-hydroxybenzoate 3-geranyltransferase is a regulat ory enzyme in the biosynthesis of shikonin, a phytoalexin and pharmace utical produced by cell cultures of Lithospermum erythrorhizon Sieb. e t Zucc.. In Linsmaier-Skoog medium, the activity of this enzyme could be enhanced more than 200-fold by addition of methyl jasmonate, and th is culture material was used for the solubilization and purification o f the enzyme. Of various detergents examined, digitonin was the most s uitable for the solubilization of the enzyme. The solubilized enzyme w as purified 800-fold by chromatography over diethylaminoethyl (DEAE)-S ephacel, Heparin-Sepharose, Reactive Green 19-Agarose, and Cholic Acid -Agarose. The purified enzyme required magnesium ions as cofactor and was highly specific for geranyldiphosphate (GPP) and 4-hydroxybenzoate (4HB) as substrates. The K-m values for 4HB and GPP were calculated b y the method of Lineweaver and Burk as 18.4 mu M and 13.8 mu M, respec tively.