ß CARBOXYLATION ENZYMES IN MARINE PHYTOPLANKTON AND ISOLATION AND PURIFICATION OF PYRUVATE CARBOXYLASE FROMAMPHIDINIUM CARTERAE(DINOPHYCEAE)1

Abstract

ABSTRACTThe diatoms,Phaeodactylum tricornutumBohlin,Cylindrotheca closteriumvar.californica(Meres.) Reim. & Lewin,Thalassiosira pseudonanaHasle & Heimdal and the prymnesiophytePavlova lutheri(Droop), Green, have been shown to contain phosphoenolpyruvate carboxykinase E.C.4.1.1.49. Another diatomChaetoceros calcitrans(Paulsen) Takano, the chlorophyteDunaliella tertiolectaButcher, a rhodophytePorphyridium cruentumNaegeli and the cyanophyteAnabaena cylindricaLemmermann, all possessed phosphoenolpyruvate carboxylases E.G.4.1.1.31, which were stimulated by Mn ions and inhibited by malate and aspartate. Two dinoflagellates,Amphidinium carteraeHulbert andGymnodiniumsp., were shown to contain pyruvate carboxylase E.G.6.4.1.1., not previously reported in plants or marine algae. Pyruvate carboxylase was isolated and purified and found to contain biotin and it was inhibited by avidin and could be distinguished from the other two enzymes by complete inhibition by 5 mM Mn ions. The β carboxylating enzymes account for the anaplerotic formation of amino acids and intermediates of the tricarboxylic acid cycle formed during short‐term fixation of CO2.