Isolation and characterization of NADP+-linked isocitrate dehydrogenase of germinating pea seeds (Pisum sativum).
Indian J Biochem Biophys
;
2001 Oct; 38(5): 335-41
Article
Dans Anglais
| IMSEAR
| ID: sea-27071
ABSTRACT
NADP+-linked isocitrate dehydrogenase (E.C.1.1.1.42) has been purified to homogeneity from germinating pea seeds. The enzyme is a tetrameric protein (mol wt, about 146,000) made up of apparently identical monomers (subunit mol wt, about 36,000). Thermal inactivation of purified enzyme at 45 degrees and 50 degrees C shows simple first order kinetics. The enzyme shows optimum activity at pH range 7.5-8. Effect of substrate [S] on enzyme activity at different pH (6.5-8) suggests that the proton behaves formally as an "uncompetitive inhibitor". A basic group of the enzyme (site) is protonated in this pH range in the presence of substrate only, with a pKa equal to 6.78. On successive dialysis against EDTA and phosphate buffer, pH 7.8 at 0 degrees C, yields an enzymatically inactive protein showing kinetics of thermal inactivation identical to the untreated (native) enzyme. Maximum enzyme activity is observed in presence of Mn2+ and Mg2+ ions (3.75 mM). Addition of Zn2+, Cd2+, Co2+ and Ca2+ ions brings about partial recovery. Other metal ions Fe2+, Cu2+ and Ni2+ are ineffective.
Texte intégral:
Disponible
Indice:
IMSEAR (Asie du Sud-Est)
Sujet Principal:
Graines
/
Sites de fixation
/
Chromatographie sur DEAE-cellulose
/
Chromatographie sur gel
/
Pisum sativum
/
Germination
/
Électrophorèse sur gel de polyacrylamide
/
Température élevée
/
Concentration en ions d'hydrogène
/
Isocitrate dehydrogenases
langue:
Anglais
Texte intégral:
Indian J Biochem Biophys
Année:
2001
Type:
Article
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