title: Chromatographic and immunological evidence that chloroplastic and cytosolic pea (Pisum sativum L.) NADP-isocitrate dehydrogenases are distinct isoenzymes.
abstract: Two NADP-isocitrate dehydrogenase isoenzymes designated as NADP-IDH1 and NADP-IDH2 (EC 1.1.1.42) were identified in pea (Pisum sativum) leaf extracts by diethylaminoethylcellulose chromatography. The predominant form was found to be NADP-IDH1 while NADP-IDH2 represented only about 4% of the total leaf enzyme activity. These enzymes share few common epitopes as NADP-IDH2 was poorly recognized by the specific polyclonal antibodies raised against NADP-IDH1, and as a consequence NADP-IDH2 does not result from a post-translational modification of NADP-IDH1. Subcellular fractionation and isolation of chloroplasts through a Percoll gradient, followed by the identification of the associated enzymes, showed that NADP-IDH1 is restricted to the cytosol and NADP-IDH2 to the chloroplasts. Compared with the cytosolic isoenzyme, NADP-IDH2 was more thermolabile and exhibited a lower optimum pH. The data reported in this paper constitute the first report that the chloroplastic NADP-IDH and the cytosolic NADP-IDH are two distinct isoenzymes. The possible functions of the two isoenzymes are discussed.
authors.affiliation: Physiologie Végétale Moléculaire URA CNRS D 1128, Université Paris Sud, Bâtiment 430, F-91405, Orsay Cedex, France.
authors.forename: R D
authors.initials: RD
authors.lastname: Chen
authors.forename: E
authors.initials: E
authors.lastname: Bismuth
authors.forename: M L
authors.initials: ML
authors.lastname: Champigny
authors.forename: P
authors.initials: P
authors.lastname: Gadal