Mevalonate activating enzymes and phosphatases in higher plants

The pH optima of mevalonate kinase and phosphatases in green leaves, cotyledons and chloroplasts of French bean, and in green leaves and chloroplasts of maize, have been studied. Whereas in chloroplasts the pH optimum for mevalonate kinase is at pH 7·5 with little or no activity at pH 5·5, there is with leaf and cotyledon preparations appreciable activity at the lower pH. Under some circumstances isoelectric focusing studies have given fractions showing mevalonate kinase activity at only pH 7·5 or 5·5. Acid phosphatase and ATPase activity in preparations is maximal at pH 5·5 and is much reduced in the presence of high levels of phosphate. Other investigations reported concern the stability of mevalonate kinase and phosphatase activity at pH 5·5 and 7·5 on ageing of extracts, and the activity of mevalonate kinase on greening of etiolated French bean cotyledons. The influence of metal cofactors and fluoride on mevalonate kinase and phosphatase are reported.