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 th

SUBMITTER: Detarsio E 

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

REPOSITORIES: biostudies-literature