title: The control of NAD specific malic enzyme from cauliflower bud mitochondria by metabolites.
abstract: NAD malic enzyme (EC. 1.1.1.39) has been purified from cauliflower (Brassica oleracea. var. botrytis) bud mitochondria. The enzyme exhibits complex regulatory properties being activated by a variety of metabolites including glycolytic intermediates, CoA, sulphate and Krebs cycle acids-the tricarboxylic acids with the exception of citrate being more effective than dicarboxylic acids. Fructose diphosphate which is a positive effector of the enzyme increases the affinity of the enzyme for L-malate.The enzyme is inhibited by glutamate, aspartate, phosphate and ATP, in the latter case the inhibition is largely due to chelation of Mg(2+). The plot of rate versus malate concentration is sigmoid at pH 7.0 with Mg(2+) but normal Michaelis-Menten kinetics are observed with Mn(2+). The molecular weight of the enzyme as measured by gel filtration is ca. 400000. The physiological significance of the responses to metabolites is discussed.
authors.affiliation: School of Biological Sciences, University of East Anglia, NR4 7TJ, Norwich, UK.
authors.forename: D D
authors.initials: DD
authors.lastname: Davies
authors.forename: K D
authors.initials: KD
authors.lastname: Patil