Characterization of NADP-Isocitrate Dehydrogenase from Nodules of Pigeonpea (Cajanus cajan) |
| |
Authors: | Amarjit Kaur Sarla P Malhotra Randhir Singh |
| |
Institution: | 1. Plant Biochemistry & Biotechnology Laboratory, Department of Chemistry and Biochemistry, CCS Haryana Agricultural University, Hisar, 125 004, India
|
| |
Abstract: | NADP-isocitrate dehydrogenase from nodules of pigeonpea (Cajanus cajan L. cv UPAS-120) was partially purified to about 57 folds and its properties were studied. The enzyme showed an absolute requirement for a divalent cation which was fulfilled either by Mn+2 or Mg+2 and to a smaller extent by Co+2. The enzyme exhibited a sigmoidal response to increasing concentrations of Mn2+ (S0.5=0.3mM). The apparent Km values for isocitrate, NADP and Mg2+ were 21, 23 and 280 μM, respectively. It had an optimum pH of 8.0–8.2. The enzyme activity was not affected by various organic acids, amino acids and amides. NADH inhibited the activity non-competitively with respect to NADP. An apparent inhibition by ATP and ADP was due to chelation of divalent cation. NADPH acted competitively against NADP and non-competitively against isocitrate. Glutamate caused uncompetitive inhibition with respect to NADP and competitive against isocitrate. Kinetic studies suggested the reaction mechanism to be probably random sequential. Possible regulation of the enzyme activity in the nodules via cellular redox state and the levels of reaction products is discussed. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|