ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
NADP+-malic enzyme (l-malate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.40) from pod walls of chickpea was purified 51-fold by ammonium sulphate fractionation, DEAE- cellulose chromatography and gel filtration through Sepharose 4B. The purified enzyme required a divalent cation, either Mn2+ or Mg2+, for its activity. Km values at pH 7.8 for malate, NADP+ and Mn2+ were 4.0, 0.031 and 0.71 mM, respectively. Mn2+-dependent activity was inhibited by heavy metal ions such as Cd2+, Zn2+, Hg2+, and to a lesser extent by Pb2+ and Al3+. Among the organic acids examined, sodium salts of oxalate and oxaloacetate were inhibitory. Kinetics of the reaction mechanism showed sequential binding of malate and NADP+ to the enzyme. Products of reaction, viz. pyruvate, bicarbonate and NADPH, inhibited the enzyme activity. At limiting concentrations of NADP+, pyruvate and bicarbonate induced a positive cooperative effect by malate. It is proposed that the activity of NADP+-malic enzyme is controlled by intracellular concentrations of substrates and products.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1986.tb01931.x
Permalink