Study of the interaction between L-lactate dehydrogenase isoenzymes and immobilized 8-substituted adenosine 5'-monophosphate by means of affinity electrophoresis

Affinity electrophoresis and its applications to studies of immune response

Affinity electrophoresis (AEP) is a useful technique for separation of biomolecules such as plasma proteins, enzymes, nucleic acids, lectins, receptors, and extracellular matrix proteins by specific interactions with their ligands in electric fields and for the determination of dissociation constants for those interactions. Two-dimensional affinity electrophoresis (2-D AEP), which was newly developed by a combination of isoelectric focusing with AEP, has been used for studies on immune response to haptens. Antihapten antibodies, which were induced by immunization of a mouse with the hapten-conjugated bovine serum albumin, were separated by 2-D AEP into a large number of groups of IgG spots with a few microliters of antiserum. Each group of spots showed an identical affinity for the hapten but different isoelectric points as in the case of monoclonal antibodies specific to the hapten. This enabled us to study the diversification and affinity maturation of antihapten antibodies in the course of immunization of a single mouse. Furthermore, effects of a carrier and a hapten array on the production of antihapten antibodies and the cause of charge heterogeneity of monoclonal antibodies were also examined to understand the molecular basis of the immune response in vivo.

Study of the interaction between NADP-dependent dehydrogenase and immobilized adenosine 2'-monophosphate by means of affinity electrophoresis

A water-soluble 8-substituted adenosine 2'-monophosphate-polyacrylamide (8-sub-2'-AMP-PA) was prepared as a new affinity ligand for the determination of the dissociation constants of the interactions between immobilized 8-sub-2'-AMP and NADP-dependent dehydrogenases (NADP-dependent DH), NAD-dependent dehydrogenases (NAD-dependent DH) and phosphorylase by means of affinity electrophoresis. From the dissociation constants, it was found that NADP-dependent DH had a much stronger affinity to immobilized 8-sub-2'-AMP than did NAD-dependent DH and phosphorylase. On the other hand, NADP-dependent DH had a much weaker affinity to immobilized 8-sub-5'-AMP than did NAD-dependent DH. The effects of NADP+ and NAD+ on the interaction between immobilized 8-sub-2'-AMP and NADP-dependent DH were also investigated by means of affinity electrophoresis. NADP+ inhibited the interaction specifically, but NAD+ did not inhibit the interaction. These results indicate that 8-sub-2'-AMP binds to the coenzyme binding site of NADP-dependent DH, while other compounds, such as 8-sub-5'-AMP and NAD+, do not bind to NADP-depenndent DH. Such a difference suggests that the phosphate group at position 2' in 2'-AMP and NADP+ is important for the binding at the coenzyme binding site of NADP-dependent DH.