Changes in the Characteristics of NADP-dependent Isocitrate Dehydrogenase from Banana Fruit during Postharvest Ripening

Abstract

Changes in the activity and some characteristics of NADP-dependent isocitrate dehydrogenase (NADP-IDH, EC 1. 1. 1. 42) of banana [Musa spp (AAA group, Cavendish subgroup)] fruit during postharvest ripening were investigated. The activity was about 2.7-fold higher in yellow (ripe) fruit than in mature green fruit. These activities were NADP-dependent in both stages of fruit, but the degree of Mg2+ dependency was slightly higher in mature green fruit than in yellow fruit. The Km values of the enzyme for DL-isocitrate in mature green and yellow fruit were 48. 4μM and 59.5μM, respectively. While the value for NADP+ in mature green fruit was 6.14μM, that was 11.56μM in yellow one. The elution pattern of gel filtration showed that yellow fruit have different peaks for these activities from mature green fruit. From these results, NADP-IDH in banana fruit may change their isozymes which have different Km values during postharvest ripening.