Molecular Properties of NADP-dependent Malate Dehydrogenase

Abstract

NADP-dependent malate dehydrogenase (E. C.1.1.1.82) is located exclusively in the chloroplasts of C₃-, C₄- and CAM-plants (Hatch, Slack, 1969). The activity of the enzyme is completely dependent on photosynthetic electron flow or reduction by dithiothreitol (Johnson, Hatch, 1970; Anderson, Avron, 1976; Wolosiuk et al. 1977). Several protein factors are involved in the modulation from the inactive to the active enzyme (for review see: Buchanan 1980), which has been proposed to be a reductive process at protein disulfides (Jacquot et al. 1980). In this paper a rapid, high yield purification procedure for the isolation of homogeneous NADP-MDH of high specific activity from a C₃-plant is presented. Some kinetic and molecular properties of the purified enzyme are described and the activation process is characterized.