Cloning, expression, and purification of a functional glutathione reductase from sweet potato (Ipomoea batatas [L.] Lam): kinetic studies and characterization

Cloning, expression, and purification of a functional glutathione reductase from sweet potato (Ipomoea batatas [L.] Lam): kinetic studies and characterization

2009

A:PS

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 (beta-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 degrees C was 3.3 min, and its thermal inactivation rate constant Kd was 3.48x10-1 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.

v.57(10):4403-4408, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

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