Immunoadsorption of histidinol dehydrogenase in the presence of urea

Urea inhibits the activity of histidinol dehydrogenase from Escherichia coli B, prevents precipitation of the enzyme by specific antibodies and dissolves immunoprecipitates which were formed in the absence of urea. However, immunoadsorption of the enzyme to Sepharose-bound antibodies can take place in the presence of high concentrations (5-8 M) of urea. The immobilized antibody-bound enzyme exhibits almost full activity after removal of the urea and is inhibited by soluble specific antibodies in the presence of urea. The possibility of using immunoadsorption in the presence of urea for the study of insoluble proteins is discussed.