Light activation of NADP malic enzyme in leaves of maize: marginal increase in activity, but marked change in regulatory properties of enzyme.

This article reports the characteristics of light activation of NADP-malic enzyme (NADP-ME, EC 1.1.1.40) in leaf discs of maize (Zea mays cv. VMH 404) for the first time. The leaf discs were illuminated in the presence of 2 mmol/L bicarbonate, as light activation increases in the presence of bicarbonate. Upon illumination, the Vmax of NADP-ME increased by about 30%. Although small, the increase was consistent and significant. The changes in regulatory properties of NADP-ME were quite pronounced. The extent of light activation was similar when substrate (malate) concentration was either 4 mmol/L (saturating) or 0.01 mmol/L (limiting). There was only a marginal change in the Km for malate, but there was marked change in the response of NADP-ME to activators or inhibitors. The Ki for pyruvate and oxalate increased by 100 and 67% respectively, while the Ka for the citrate and succinate increased by 36 and 32% respectively. These results suggest that the NADP-ME becomes less sensitive to feedback inhibition on illumination. The light-induced change seems to be due, at least partially, to the reduction of dithiols, as incubation of leaf extracts with DTE dampened light activation of NADP-ME. We conclude that the properties of NADP-ME do change on illumination. Although there was only a marginal increase in the activity of the enzyme on illumination of leaf discs, the changes in regulatory properties of NADP-ME were marked.

[1]  G. Edwards,et al.  Malate metabolism by NADP-malic enzyme in plant defense , 1999, Photosynthesis Research.

[2]  A. S. Raghavendra,et al.  Molecular biology of C4 phosphoenolpyruvate carboxylase: Structure, regulation and genetic engineering , 1994, Photosynthesis Research.

[3]  P. Pupillo,et al.  Two forms of NADP-dependent malic enzyme in expanding maize leaves , 2004, Planta.

[4]  W. Campbell.  NITRATE REDUCTASE STRUCTURE, FUNCTION AND REGULATION: Bridging the Gap between Biochemistry and Physiology. , 1999, Annual review of plant physiology and plant molecular biology.

[5]  J. Vidal,et al.  Regulatory phosphorylation of C4 PEP carboxylase , 1997 .

[6]  Sanjay Kumar Gupta,et al.  NADP-malic enzyme: immunolocalization in different tissues34 plant maize and the C3 plant wheat , 1997 .

[7]  H. Bohnert,et al.  Molecular Genetics of Crassulacean Acid Metabolism , 1997, Plant physiology.

[8]  Steven C. Huber,et al.  ROLE AND REGULATION OF SUCROSE-PHOSPHATE SYNTHASE IN HIGHER PLANTS. , 1996, Annual review of plant physiology and plant molecular biology.

[9]  V. Maurino,et al.  NADP-malic enzyme isoforms in maize leaves. , 1996, Biochemistry and molecular biology international.

[10]  S. Holtgrefe,et al.  Redox equilibria between the regulatory thiols of light/dark-modulated chloroplast enzymes and dithiothreitol: fine-tuning by metabolites. , 1995, Biochimica et biophysica acta.

[11]  M. F. Drincovich,et al.  Redox regulation of maize NADP-malic enzyme by thiol-disulfide interchange: effect of reduced thioredoxin on activity. , 1994, Biochimica et biophysica acta.

[12]  G. Edwards,et al.  C4 Photosynthesis (The CO2-Concentrating Mechanism and Photorespiration) , 1993, Plant physiology.

[13]  R. Leegood,et al.  Plant Biochemistry and Molecular Biology , 1993 .

[14]  R. Sage,et al.  Regulation of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Activity in Response to Reduced Light Intensity in C4 Plants , 1993, Plant physiology.

[15]  G. Edwards,et al.  NADP-malic enzyme from plants. , 1992 .

[16]  M. F. Drincovich,et al.  A study on the inactivation of maize leaves nadp-malic enzyme by 3-bromopyruvate , 1992 .

[17]  R. Furbank,et al.  Mechanism of c(4) photosynthesis: a model describing the inorganic carbon pool in bundle sheath cells. , 1989, Plant physiology.

[18]  T. Nelson,et al.  Primary structure of the maize NADP-dependent malic enzyme. , 1989, The Journal of biological chemistry.

[19]  Holaday As,et al.  Effect of pH on the Kinetic Parameters of NADP-Malic Enzyme from a C4Flaveria (Asteraceae) Species , 1989 .

[20]  A. Iglesias,et al.  Purification of NADP-Malic Enzyme and Phosphoenolpyruvate Carboxylase from Sugar Cane Leaves , 1989 .

[21]  P. Pupillo,et al.  Isoforms of NADP-dependent Malic Enzyme in Tissues of the Greening Maize Leaf , 1988 .

[22]  R. Furbank,et al.  Mechanism of c(4) photosynthesis: the size and composition of the inorganic carbon pool in bundle sheath cells. , 1987, Plant physiology.

[23]  R. Scheibe.  NADP+‐malate dehydrogenase in C3‐plants: Regulation and role of a light‐activated enzyme , 1987 .

[24]  N. Jawali,et al.  Presence of essential histidine residues in nadp-malic enzyme from maize , 1987 .

[25]  D. Davies.  The fine control of cytosolic pH , 1986 .

[26]  Hitoshi Nakamoto,et al.  Pyruvate,Pi Dikinase and NADP-Malate Dehydrogenase in C4 Photosynthesis: Properties and Mechanism of Light/Dark Regulation , 1985 .

[27]  S. K. Suneja,et al.  Properties of NADP-malic enzyme from glumes of developing wheat grains , 1985 .

[28]  D. Hague,et al.  Light-stimulated synthesis of NADP malic enzyme in leaves of maize. , 1983, The Journal of biological chemistry.

[29]  B. Halliwell,et al.  The Biochemistry of plants : a comprehensive treatise , 1981 .

[30]  G. Edwards,et al.  6 – The C4 Pathway , 1981 .

[31]  B. Buchanan.  Role of light in the regulation of chloroplast enzymes Annu Rev Plant Physiol 31: 341-374 , 1980 .

[32]  T. Akazawa,et al.  NADP-malic enzyme from maize leaf: purification and properties. , 1979, Archives of biochemistry and biophysics.

[33]  Professor Dr. M. Kluge,et al.  Crassulacean Acid Metabolism , 1978, Ecological Studies.

[34]  D. Arnon.  COPPER ENZYMES IN ISOLATED CHLOROPLASTS. POLYPHENOLOXIDASE IN BETA VULGARIS. , 1949, Plant physiology.