Intrachloroplastidic mevalonate-activating enzymes in plant cells

Abstract

Mevalonate phosphorylation by chloroplasts from Spinacia oleracea leaves, Agave americana leaves and Pinus pinaster seedlings is reported. Different modifications in the technique of chloroplast isolation by using an aqueous method have been introduced in order to protect the mevalonate kinase and phosphomevalonate kinase activities. The acid pH values of the preparations obtained by conventional methods from Agave americana and Pinus pinaster decrease their kinase activities; therefore, 0.35 M TrisHCl buffer, pH 7.9, containing 0.35 M mercaptoethanol must be used as the isolation medium. Ultrasonic treatment has been found to be the best method for chloroplast disruption in Spinacia oleracea and Agave americana, but a considerable inactivation of mevalonate kinase from Pinus pinaster has been observed after this treatment. The time course of mevalonic acid (MVA) phosphorylation by intrachloroplastidic enzymes was studied. Preparations from etiolated leaves of Agave americana also phosphorylated MVA, but their plastids are more fragile than those from green leaves.