Molecular cloning and characterization of a cDNA encoding pea monodehydroascorbate reductase.

作者：Siva S. Murthy, Barbara A. Zilinskas · 发表于：Journal of Biological Chemistry · 年份：1994 · DOI：10.1016/s0021-9258(18)47399-1 · 被引用次数：63 · 研究领域：GABA and Rice Research、Vitamin C and Antioxidants Research、Protein Hydrolysis and Bioactive Peptides

Monodehydroascorbate radicals are generated in plant cells enzymatically by the hydrogen peroxide scavenging enzyme, ascorbate peroxidase, and nonenzymatically via the univalent oxidation of ascorbate by superoxide, hydroxyl, and various organic radicals. Regeneration of ascorbate is achieved by monodehydroascorbate reductase (EC 1.6.5.4) using NAD(P)H as an electron donor or, alternatively, by a set of two coupled reactions requiring dehydroascorbate reductase, glutathione reductase, glutathione, and NAD(P)H. As monodehydroascorbate reductase is a key enzyme in maintaining reduced pools of ascorbate, an important antioxidant, we undertook this study to learn more about its structure, function, and regulation. Herein we report the molecular cloning and characterization of a cDNA encoding monodehydroascorbate reductase of pea (Pisum sativum L.). The cDNA encodes a 433-amino acid polypeptide that shows, respectively, 73 and 87% identity with peptide fragments from soybean and cucumber monodehydroascorbate reductase. Monodehydroascorbate reductase contains the NAD(P)H and FAD binding domains of other flavin oxidoreductases. The cloned enzyme lacks a transit peptide, but the sequence of the carboxyl terminus is Ser-Lys-Ile, similar to the targeting motif found in peroxisomal proteins. When expressed in Escherichia coli fused to maltose-binding protein, monodehydroascorbate reductase has enzymatic properties comparable with purified soybean and cucumber monodehydroascorbate reduct...