Background

Numerous studies have shown that the intracellular redoxpotential of the cell is important to cell growth. Cellular redoxpotential can be determined by the amounts of the reduced coenzymeNADPH, a principal product of the oxidative branch of the pentosephosphate pathway (PPP). The investigators in the study presentedhere sought to demonstrate links between the activity of the enzymeglucose-6-phosphate dehydrogenase (G6PD) activity, cellular NADPHconcentrations, and rates of cell growth. Previous studies haveshown that the glucose-6- phosphate dehydrogenase enzyme can beactivated on the order of minutes or even seconds, possibly throughthe action of growth factors that release a bound, inactive G6PD tothe cytosol, where, via a mechanism that might involve tyrosinephosphorylation of a membrane-bound receptor, the unbound G6PDtranslocates to the cytosol and becomes active.

NADPH is important to the cell in a variety of ways. The reducedcoenzyme can react with potential damaging oxidizing agents,ridding the cell of these agents before they can damage importantcellular components.

Question

List general cellular mechanisms that would affect the activityof G6PD. Which of these mechanisms would result in long-term (onthe order of minutes to hours) vs. short-term (minutes to seconds)regulation of the enzyme's activity?