Structural and kinetic characterization of a maize aldose reductase.
The aldo-keto reductases (AKRs) are classified as oxidoreductases and are found in organisms from prokaryotes to eukaryotes. The AKR superfamily consists of more than 120 proteins that are distributed throughout 14 families. Very few plant AKRs have been characterized and their biological functions remain largely unknown. Previous work suggests that AKRs may participate in stress tolerance by detoxifying reactive aldehyde species. In maize endosperm, the presence of an aldose reductase (AR; EC 1.1.1.21) enzyme has also been hypothesized based on the extensive metabolism of sorbitol. This manuscript identifies and characterizes an AKR from maize (Zea mays L.) with features of an AR. The cDNA clone, classified as AKR4C7, was expressed as a recombinant His-tag fusion protein in Escherichia coli. The product was purified by immobilized metal affinity chromatography followed by anion exchange chromatography. Circular dichroism spectrometry and SAXS analysis indicated that the AKR4C7 protein was stable, remained folded throughout the purification process, and formed monomers of a globular shape, with a molecular envelope similar to human AR. Maize AKR4C7 could utilize dl-glyceraldehyde and some pentoses as substrates. Although the maize AKR4C7 was able to convert sorbitol to glucose, the low affinity for this substrate indicated that AKR4C7 was probably a minimal contributor to sorbitol metabolism in maize seeds. Polyclonal antisera raised against AKR4C7 recognized at least three AR-like polypeptides in maize kernels, consistent with the presence of a small gene family. Diverse functions may have evolved for maize AKRs in association with specific physiological requirements of kernel development.
de Sousa
Sylvia Morais
SM
Centro de Biologia Molecular e Engenharia Genética, Departamento de Genética e Evolução, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.
Rosselli
Luciana K
LK
Kiyota
Eduardo
E
da Silva
Julio César
JC
Souza
Gustavo H M F
GH
Peroni
Luis Antonio
LA
Stach-Machado
Dagmar R
DR
Eberlin
Marcos N
MN
Souza
Anete P
AP
Koch
Karen E
KE
Arruda
Paulo
P
Torriani
Iris L
IL
Yunes
José Andrés
JA
D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D000449:Aldehyde Reductase; D000074408:Aldo-Keto Reductases; D000595:Amino Acid Sequence; D018076:DNA, Complementary; D017343:Genes, Plant; D008969:Molecular Sequence Data; D013012:Sorbitol / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics
D018076:DNA, Complementary; D013012:Sorbitol; D000429:Alcohol Oxidoreductases; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase