Biosynthesis of terpenes: III. Mevalonic kinase from higher plants

Abstract Mevalonic kinase activity has been demonstrated in extracts from several plant species. Pumpkin ( Cucurbita pepo ) seedlings had the highest activity of the various plant materials tested, and they were therefore used as a source of the enzyme for further investigations. Mevalonic kinase from pumpkin seedlings was partially purified, and its properties were investigated. Maximum activity is obtained with ATP as the phosphate donor, though several other nucleotides can also be utilized. A divalent metal ion is required: Mn 2+ is the most effective, but several others, including Mg 2+ , can replace it. The optimum pH for the enzyme is about 5.7. The enzyme remains in the supernatant solution after fractionation of the cell components by centrifugation, suggesting that it is associated with the soluble cytoplasm. The product of the enzymic reaction contains by analysis one mole of phosphate per mole of mevalonate, and gives R F values in paper chromatography which agree with published values for 5-phosphomevalonic acid. With crude enzyme extracts this product is partly converted into a second derivative, which is tentatively identified, from R F values, as 5-pyrophosphomevalonic acid.