Studies on the conjugation of horseradish peroxidase to immunoglobulin G via glutaraldehyde

Abstract

Horseradish peroxidase was conjugated to immunoglobulin G via glutaraldehyde by a two-step procedure using an increasing excess of peroxidase in the second step reaction. The yield of conjugated monomeric IgG and the amount of free IgG were analyzed by SDS-polyacrylamide electrophoresis and gel-filtration. The antigen binding capacity of the enzyme-antibody conjugates was evaluated by radial immunodiffusion. Conjugation of peroxidase to IgG with a 1:20 molar:molar excess of glutaraldehyde-activated peroxidase resulted in a high yield of conjugated IgG without any detectable amounts of polymers of IgG or residual free IgG. The antigen binding capacity of the conjugate varied between different antigen-antibody systems, but in general it was not significantly different from that of native IgG. The enzyme activity was reduced to 70% of the activity of native peroxidase.