NAD‐malic enzyme from plants

Abstract

NAD‐malic enzyme (NAD‐ME) is a primary regulatory enzyme for the metabolism of malate in plant mitochondria. NAD‐ME serves an anaplerotic function for the production of pyruvate, and provides CO 2 for refixation in the Calvin cycle in certain C 4 and Crassulacean acid metabolism plants. Clues regarding the mechanism of control of NAD‐ME in vivo come from numerous studies on the physical and kinetic properties of the enzyme. The kinetics are complex and are altered by the pH of the assay medium as well as by serveral effectors, including divalent cations. CoA, sulfate, acetyl CoA, and fructose 1,6‐bisphosphate (activators) and chloride, citrate, and bicarbonate (inhibitors). The enzyme is functional as a dimer, tetramer and octamer and the variation in kinetics is at least in part due to its association/dissociation.