Changes in NADP-linked isocitrate dehydrogenase activity during postharvest ripening of banana fruit

Abstract

The changes in activity of NADP-linked isocitrate dehydrogenase (NADP-IDH, EC 1.1.1.42) of banana fruit (Musa spp. [AAA group, Cavendish subgroup]) during postharvest ripening were investigated. The activity of NADP-IDH in the flesh of mature green fruit was low during the preclimacteric stage at 20°C. However, the enzyme activity in fruit treated with propylene increased during ripening to more than twice that of the control. The contents of pyruvate and 2-oxoglutarate also increased in propylene treated fruit. The increase in 2-oxoglutarate is attributed to the rise in NADP-IDH activity because they both coincided with the increase of respiration rate during postharvest ripening. Hence, NADP-IDH is considered to play an important role in the postharvest ripening of banana fruit.