Abstract:A cDNA encoding a putative glutathione reductase (GR) was cloned from sweet potato (Ib). The deduced protein showed high level of sequence homology with GRs from other plants (79−38%). A three-dimensional (3-D) homology structure was created. The active site Cys residues are conserved in all reported GR. Functional IbGR was overexpressed and purified. The purified enzyme showed an active monomeric form on a 10% native polyacrylamide gel electrophoresis (PAGE). The monomeric nature of the enzyme was confirmed by sodium dodecyl sulfate−polyacrylamide gel electrophoresis (SDS−PAGE) and molecular mass determination of the native enzyme. The Michaelis constant (Km) values for GSSG (glutathione disulfide) and NADPH (β-nicotinamide adenine dinucleotide phosphate, reduced form) were 0.114 and 0.056 mM, respectively. The enzyme activity was inhibited by Cu2+ and Zn2+, but not by Ca2+. The protein’s half-life of deactivation at 70 °C was 3.3 min, and its thermal inactivation rate constant Kd was 3.48 × 10−1 min−1. The enzyme was active in a broad pH range from 6.0 to 11.0 and in the presence of imidazole up to 0.8 M. The native enzyme appeared to be resistant to digestion by trypsin or chymotrypsin.