Structure and Association of Glutamate Dehydrogenase Solutions

Abstract

Our studies of bovine liver glutamate dehydrogenase (GDH) solutions by physico-chemical methods may be divided into two distinct pursuits: (a) the structure of the active enzyme oligomer, with special reference to the number of subunits per oligomer macromolecule and their spatial arrangement, and (b) the reversible association of the enzyme under various experimental conditions (changes in concentration and addition of coenzyme and regulatory reagents) to form highly polymerized structures in solution. The ultimate aim of any research of this type is, without doubt, obtainment of basic and reliable information useful in the furthering of our understanding of the structure and function of the enzyme in its natural biological surroundings. The readily effected, concentration dependent, polymerization-depolymerization reaction is related to subtle changes in the substrate specificity of the active enzyme. It appears that the oligomer is capable of existing in at least two active forms with distinct substrate activity, but that only one of these forms is able to polymerize. The state and mechanism of aggregation of the enzyme are thus of great interest, particularly in view of the fact that the enzyme is believed to exist at high concentrations in its native and active form in the mitochondria of the liver.