Amino Acid Sequence and Molecular Weight of Native NADP Malate Dehydrogenase from the C₄ Plant Zea mays

Abstract

N-terminus amino acid analysis of purified corn (Zea mays) NADP malate dehydrogenase showed that the mature protein begins at serine-41 of the preprotein sequence and not threonine-58 as previously concluded; therefore, the transit peptide consists of 40 amino acids. The theoretical molecular weight of the mature subunit protein (392 amino acids) is 42,564, agreeing with an experimental value of about 43,000. The molecular weight of the native unactivated (dark form) and activated (light form) of NADP malate dehydrogenase, determined by analytical ultracentrifugation analysis, was about 84,000, indicating that both forms are dimers. However, conventional and high performance liquid chromatography gel filtration procedures indicated apparent molecular weights of about 110,000 to 120,000 for the unactivated native enzyme and about 143,000 to 150,000 for the active enzyme; in these cases, the molecular weight may be overestimated due to the effect of an unusual molecular conformation on the mobility of the enzyme. 57 amino acids. The present study reports that the native Z. mays NADP-MDH is in fact 17 amino acids longer at the Nterminal end and, hence, contains 392 amino acids. Further information is also provided about the subunit mol wt and the origin and significance of the discrepancies between reported mol wts of the native forms of the enzyme.

Bilevel Disulfide Group Reduction in the Activation of C4 Leaf Nicotinamide Adenine Dinucleotide Phosphate-Malate Dehydrogenase

“…However, a second, more readily reduced S-S (higher redox potential), termed here the preregulatory S-S, must first be reduced to give a form of NADP-MDH that can be activated by ThR-m, possibly as a result of a conformational change in the enzyme or a change in how the subunits of the dimeric enzyme interact with each other. The lag in activation of NADP-MDH is unlikely to be due to changes in the oligomeric state of the enzyme because both the active and unactivated forms of the enzyme are apparently dimers (1,17). It is interesting in this connection that both unactivated NADP-MDH and especially active NADP-MDH have unusual molecular conformations, as judged by their behavior during gel filtration (1).…”

Cloning, site‐specific mutagenesis, expression and characterization of full‐length chloroplast NADP‐malate dehydrogenase from Pisum sativum

“…As has recently been shown for the homologous enzyme from Sorghum vulgare and Zea mags, the N-terminal sequence of NADP-MDH is easily accessible to proteolysis so that cleavage during purification may lead to truncated final products (Kagawa and Bruno, 1988; Crktin et a]., 1990; Agostino et al, 1992). Preliminary experiments.…”