Inhibition of lobster-muscle arginine kinase by homologous antibodies and study of an antibody population directed against a tyrosine-containing antigenic structure.

The effect of highly inhibitory rabbit antibodies on the enzymic activity of lobster-muscle arginine kinase has been studied. 100% inhibition was obtained at a 30-fold molar excess of antibody. The guanidine substrate L-arginine did not protect the enzyme from subsequent inhibition by its antibodies. On the other hand, the metal-nucleotide substrate Mg-ATP, or the substrate analog Mg-AMP, protected about 50% the enzyme activity, the extent of hte protection being irrespective of hte presence or of the absence of L-arginine and of the value of the molar ration Ab/Ag/ An antibody population directed against the antigenic determinant containing the essential tyrosine residue of the enzyme has been isolated by the affinity chromatography. No inhibitory acitivity was found in that fraction. Most of the inhibitory activity was found in the remaining antibody populations...