NADP(-ISOCITRATE DEHYDROGENASE IN GERMINATING AND SENESCING PUMPKIN COTYLEDONS())

NADP(+)-isocitrate dehydrogenase (IDH, EC 1.1.1.42) was studied during the post germinative growth of pumpkin (Cucitrbita pepo L. cv. Albere llo di Sarzana) seedlings. In cotyledons, IDH activity increased in th e dark and declined after illumination. Native PAGE showed that at lea st two isozymes of low electrophoretic mobility are present in cotyled ons and absent in other pumpkin tissues. Anion exchange chromatography performed on extracts both from 4-day-old etiolated cotyledons and fr om illuminated cotyledons confirmed the trend of the IDH isoforms. In senescing cotyle dons an additional IDH isoform with higher electropho retic mobility appears. Overall the data indicate the presence of spec ific NADP(+)-IDH isoforms in etiolated cotyledons and senescing cotyle dons, when glyoxylate cycle enzymes are active. A possible role for th ese IDH isoforms is proposed.