title: Malate decarboxylases: evolution and roles of NAD(P)-ME isoforms in species performing C(4) and C(3) photosynthesis.
abstract: In the C(4) pathway of photosynthesis two types of malate decarboxylases release CO(2) in bundle sheath cells, NADP- and NAD-dependent malic enzyme (NADP-ME and NAD-ME), located in the chloroplasts and the mitochondria of these cells, respectively. The C(4) decarboxylases involved in C(4) photosynthesis did not evolve de novo; they were recruited from existing housekeeping isoforms. NADP-ME housekeeping isoforms would function in the control of malate levels during hypoxia, pathogen defence responses, and microspore separation, while NAD-ME participates in the respiration of malate in the tricarboxylic acid cycle. Recently, the existence of three enzymatic NAD-ME entities in Arabidopsis, occurring by alternative association of two subunits, was described as a novel mechanism to regulate NAD-ME activity under changing metabolic environments. The C(4) NADP-ME is thought to have evolved from a C(3) chloroplastic ancestor, which in turn would have evolved from an ancient cytosolic enzyme. In this way, the C(4) NADP-ME would have emerged through gene duplication, acquisition of a new promoter, and neo-functionalization. In contrast, there would exist a unique NAD-ME in C(4) plants, which would have been adapted to perform a dual function through changes in the kinetic and regulatory properties of the C(3) ancestors. In addition to this, for the evolution of C(4) NAD-ME, insertion of promoters or enhancers into the single-copy genes of the C(3) ancestors would have changed the expression without gene duplication.
authors: Botanisches Institut, Biozentrum Köln, Universität zu Köln, Zülpicher Str. 47b, D-50674 Cologne, Germany.
authors: Alexandra
authors: A
authors: Maier
authors: Martina B
authors: MB
authors: Zell
authors: Veronica G
authors: VG
authors: Maurino
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D005075:Biological Evolution; D057486:Carbon Cycle; D002736:Chloroplasts / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D010802:Phylogeny; D010944:Plants / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*
chemical_list: D008293:Malates; D020033:Protein Isoforms; C030298:malic acid; D008291:Malate Dehydrogenase; C046446:malate dehydrogenase-(oxaloacetate-decarboxylating) (NAD+); C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)