Malate enzyme fromPseudomonas putida: Some kinetic properties and function in glucose metabolism

Pseudomonas putida was grown on glucose and gluconate under different conditions with limiting amounts of carbon and nitrogen. The activities of some enzymes were determined in the periplasmic and intracellular fractions. The results indicate that malate enzyme (l-malate: NADP⁺ oxidoreductase, oxalacetate-decarboxylating EC 1.1.1.40) may function either as an NADPH-generating system or one of intracellular hydrogen transport. For determination of the effect of NADPH and the probable reaction mechanism by which NADPH produces this effect, kinetic studies with the purified enzyme were carried out. Malate enzyme showed hyperbolic saturation curves with respect to both substrates, malate and NADP, with Km values of 7.73 (±1.8)×10^–2 mM and 1.08 (±0.3) mM for NADP andl-malate, respectively, obtained by double reciprocal plots.