Open AccessPigeon‐Liver NAD Kinase
Author(s) -
APPS David K.
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02184.x
Subject(s) - nad+ kinase , biochemistry , substrate (aquarium) , enzyme , homogeneous , chemistry , biology , thermodynamics , ecology , physics
NAD kinase was purified from pigeon liver by an improved procedure which included chromatography on phosphocellulose. The resultant preparation was homogeneous as judged by gel electrophoresis, but electrofocusing gave indications of heterogeneity. The enzyme appeared to be of molecular weight 270000, and to consist of subunits of molecular weight 34000; it may therefore be an octomer. Kinetic studies over a wide range of substrate concentrations revealed departures from Michaelis‐Menten behaviour with the substrate NAD ± ; these were interpreted tentatively in terms of negative homotropic interactions between identical binding sites, since thermal and chemical inactivation studies revealed no evidence for more than one type of catalytic site. The significance of the kinetics and of the type of inhibition produced by NADPH is discussed in terms of the regulation of NAD kinase activity in vivo .