Question

glutathione reductase catalyzes the following reaction:

GSSG (oxidized glutathione) + NADPH+H ----> 2GSH (reduced Glutathione)+ NADP+.

NAD+ + H + 2e --> NADH E= -0.32 V

NADP+ + H + 2e  NADPH E= -0.32 V

GSSG + + 2H + 2e  2GSH E= -0.23 V

a) Calculate delta G for glutathione reductase reaction in the direction shown using E values above

b) Suppose that a cell contained an isoform of glutathione reductase that used NADH instead of NADPH as the reductive coenzyme. Would you expect delta G for this enzyme to be higher, lower, or the same as the corresponding value for the real glutathione reductase? Explain

c) Given what you know about the metabolic roles and/or intracellular concentration ratios of NAD/NADH and NADP/NADPH (refer to your answer for 2) would you expect physiology delta G (not standard state delta G0’) for this enzyme to be higher, lower, or the same as delta G for the real enzyme under intracellular condition? explain

Answer 1