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Basic residues play key roles in catalysis and NADP(+)-specificity in maize (Zea mays L.) photosynthetic NADP(+)-dependent malic enzyme.

ABSTRACT: C(4)-specific (photosynthetic) NADP(+)-dependent malic enzyme (NADP(+)-ME) has evolved from C(3)-malic enzymes and represents a unique and specialized form, as indicated by its particular kinetic and regulatory properties. In the present paper, we have characterized maize (Zea mays L.) photosynthetic NADP(+)-ME mutants in which conserved basic residues (lysine and arginine) were changed by site-directed mutagenesis. Kinetic characterization and oxaloacetate partition ratio of the NADP(+)-ME K255I (Lys-255-->Ile) mutant suggest that the mutated lysine residue is implicated in catalysis and substrate binding. Moreover, this residue could be acting as a base, accepting a proton in the malate oxidation step. At the same time, further characterization of the NADP(+)-ME R237L mutant indicates that Arg-237 is also a candidate for such role. These results suggest that both residues may play 'back-up' roles as proton acceptors. On the other hand, Lys-435 and/or Lys-436 are implicated in the coenzyme specificity (NADP(+) versus NAD(+)) of maize NADP(+)-ME by interacting with the 2'-phosphate group of the ribose ring. This is indicated by both the catalytic efficiency with NADP(+) or NAD(+), as well as by the reciprocal inhibition constants of the competitive inhibitors 2'-AMP and 5'-AMP, obtained when comparing the double mutant K435/6L (Lys-435/436-->Ile) with wild-type NADP(+)-ME. The results obtained in the present work indicate that the role of basic residues in maize photosynthetic NADP(+)-ME differs significantly with respect to its role in non-plant MEs, for which crystal structures have been resolved. Such differences are discussed on the basis of a predicted three-dimensional model of the enzyme.

SUBMITTER: Detarsio E

PROVIDER: S-EPMC1133980 | biostudies-literature | 2004 Sep

REPOSITORIES: biostudies-literature

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Basic residues play key roles in catalysis and NADP(+)-specificity in maize (Zea mays L.) photosynthetic NADP(+)-dependent malic enzyme.

Detarsio Enrique E Andreo Carlos S CS Drincovich María F MF

The Biochemical journal 20040901 Pt 3

C(4)-specific (photosynthetic) NADP(+)-dependent malic enzyme (NADP(+)-ME) has evolved from C(3)-malic enzymes and represents a unique and specialized form, as indicated by its particular kinetic and regulatory properties. In the present paper, we have characterized maize (Zea mays L.) photosynthetic NADP(+)-ME mutants in which conserved basic residues (lysine and arginine) were changed by site-directed mutagenesis. Kinetic characterization and oxaloacetate partition ratio of the NADP(+)-ME K255 ...[more]

PMID: 15245332

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Project description:Food production and waste recycling are the two major issues faced globally with rapidly increasing population. Recycling organic wastes to crop amendments could be a possible solution to these issues. Earthworms transfer organic waste to compost, which is used to grow crops and increase crop productivity. This study assessed the impact of vermicompost produced from the residues of six desert plant species, i.e., (Ziziphus mauritiana, Aerva javanica, Calligonum comosum, Sacchrum benghalens, Calligonum polygonoides and Prosopis cineraria) combined with farmyard manure (5 t ha-1) on growth, yield and photosynthetic activity of maize crop. Earthworm species Eisenia fetida (Savigny, 1826) was used to prepare vermicomposting of all tested plant species. The desert species were collected from natural habitats, chopped, dried, mixed with FYM and then earthworms were released to prepare the vermicompost. The earthworms were excluded twenty days after release and resultant was considered as compost and used in the experiment. Results revealed that application of P. cineraria vermicompost resulted in the highest plant height (75.33 cm), stem diameter (22.66 mm), cob length (17.66 cm), number of grains/cob (374.67), 1000-grain weight (260.41 g) and grains yield (3.20 t/ha). Application of P. cineraria vermicompost resulted in the highest uptake of macronutrients, i.e., N (91.01%), P (22.07%), K (80.41%), micronutrients, i.e., Fe (19.07 ppm), Zn (40.05 ppm), and phenolic contents (150). Application of P. cineraria vermicompost also resulted in the highest quantum photosynthetic yield (0.42 mole C/mole of photon), chlorophyll florescence (355.18 moles of photon m-2s-1) and electron transport rate (310.18 micro mole m-2s-1). It is concluded that vermicomposting has the potential to improve growth and yield of maize crop. Particularly, application of vermicompost obtained from P. cineraria can be used to improve the growth and yield of maize crop. Nonetheless, field trials are necessary for a wide scale recommendation.

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Dataset Information

Basic residues play key roles in catalysis and NADP(+)-specificity in maize (Zea mays L.) photosynthetic NADP(+)-dependent malic enzyme.

Publications

Basic residues play key roles in catalysis and NADP(+)-specificity in maize (Zea mays L.) photosynthetic NADP(+)-dependent malic enzyme.

Similar Datasets

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