Horst Sund

Association-Dissociation Phenomena in Biopolymers

Abstract Association between biological macromolecules by non-covalent interactions is not only a wide-spread phenomenon in nature but also is of invaluable importance for life processes. In most cases the association is practically irreversible under experimentally accessible conditions, but a few examples are known where a reversible association-dissociation equilibrium can be studied. Such studies are of basic importance for the understanding of the association mechanisms and thus for the questions concerning the self-organization of living material. In addition, association-dissociation equilibria also must be assumed to play an important part in the regulative systems of the organisms. Very little data is available for the parameters of the micro-environment of the biological macromolecules in the different cell compartments, so that in vitro studies of regulative processes under a wide variety of solvent conditions are not only of academic interest. In the present review some examples of association...

Quaternary Structure and Enzymic Properties of Beef Liver Glutamate Dehydrogenase

The molecular weight of NAD-dependent dehydrogenases varies from some twenty thousands to some millions. Most of the molecular weights are in the range 50, 000 to 200, 000 (1). The subunit structure of the majority of dehydrogenases is now well established, most of them are composed of more than one polypeptide chain. All these enzymes consist of polypeptide chains with molecular weights between 14, 000 and 50, 000 (1, 2). In general only the associated molecule is observed in the native state. If this is the case it can be assumed that the self-assembly process to the associated and active molecule leads to such an important lowering of free energy that in the native state the equilibrium concentration of the single polypeptide chain is far below detectibility.