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, for retixation in the Calvin cycle in certain C, 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 effecters, 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.

Tissue-Specific and Light-Mediated Expression of the C4 Photosynthetic NAD-Dependent Malic Enzyme of Amaranth Mitochondria

“…Malic enzymes also can provide reducing equivalents for biosynthetic pathways such as fatty acid biosynthesis (Artus and Edwards, 1985). In addition to their roles as metabolic enzymes, malic enzymes have been recruited in some plants to function in certain specialized processes such as thermogenesis in species of the Araceae (ap Rees et al, 1983).…”

“…Vol. 11 2,1996 other plant species, consists of two nonidentical subunits, a and p. The two subunits can function in dimeric, tetrameric, or octameric form, with equivalent numbers of each subunit occurring in each complex (Artus and Edwards, 1985;Wedding, 1989). The two-subunit composition of plant mitochondrial NAD-MEs contrasts with that of a11 other forms of plant, animal, and bacterial malic enzymes, which occur as tetramers of a single subunit.…”

Changes in the Composition of Xylem Sap during Development of the Spadix of Skunk Cabbage (Symplocarpus foetidus)

“…39) Alternatively, malate is oxidized to pyruvate, which is subsequently utilized in the TCA cycle, by NAD þ malic enzyme that exists in plant mitochondria. 40) Furthermore, succinate is provided as a substrate for succinate dehydrogenase in the TCA cycle and a mitochondrial respiratory chain. 39,41) It was also found that the concentration of citrate was extremely low, and no significant difference was observed between the concentrations in thermogenic and post-thermogenic plants (Fig.…”

Extraction and study of enzymes linked to malate metabolism in tree leaves

“…Enzymes implicated in synthesis and catabolism of this substrate are widely distributed in the cellular compartments. If these enzymes have become well known in herbaceous plants (Macrae, 1971;Davis and Patil, 1975;Wiskich and Dry, 1985;Artus and Edwards, 1985), very few studies have been made on woody plants Cheliak, 1985, 1986;Weimar and Rothe, 1987 (Gerant et al, 1988).…”