The effect of glycerol in the storage medium on the inhibitory kinetic behavior of glutathione reductase

• Main Authors: Kulaksiz-Erkmen Gulnihal, Can Betul, Dalmizrak Ozlem, Ogus Hamdi I., Ozer Nazmi
• Format: Article
• Language: English
• Published: University of Belgrade, University of Novi Sad 2012-01-01
• Series: Archives of Biological Sciences
• Subjects: Glutathione reductase; glycerol; rat kidney; NADP+; inhibition kinetics
• Online Access: http://www.doiserbia.nb.rs/img/doi/0354-4664/2012/0354-46641201239K.pdf

In this study we report on the effect of glycerol used in storage buffers, on the inhibitory kinetic behavior of NADP+ on rat kidney glutathione reductase (rkGR) stored at -80°C in ± 10% (v/v) glycerol. At fixed [GSSG] and varied [NADPH], rkGR stored ± glycerol were inhibited competitively by NADP+. Although the addition of glycerol decreased Km (9.7 ± 0.9 μM) and Ki(NADP+) (26.6 ± 2.2 μM) for NADPH, the catalytic efficiency (kcat/Km = 2.75 x 107 M-1.s-1) was increased 1.64 fold. At fixed [NADPH] and varied [GSSG], rkGR exhibited noncompetitive (Ki = 397 ± 69 μM) and linear mixed-type (Ki = 59.6 ± 8.4 μM; Ks = 49.9 ± 3.2 μM; α = 7.74) inhibitions with and without glycerol during storage. The kcat/ Km of rkGR stored in glycerol was 5.16 x 106 M-1.s-1. Although the increase in kcat was 1.25 fold, the kcat/Km was minimally affected (1.06).