Maron, E., Departments of Biophysics and Chemical Immunology, The Weizmann Institute of Science, Rehovoth, Israel
Eshdat, Y., Departments of Biophysics and Chemical Immunology, The Weizmann Institute of Science, Rehovoth, Israel
Sharon, N., Departments of Biophysics and Chemical Immunology, The Weizmann Institute of Science, Rehovoth, Israel

Hen egg-white lysozyme, irreversibly inhibited by the affinity label 2′,3′-epoxypropyl β-glycoside of di(N-acetyl-d-glucosamine) ((GlcNAc)2), reacted with goat anti-hen lysozyme antibodies in the "chemically modified bacteriophage" assay as hen lysozyme and as the enzyme in the presence of a large excess of (GlcNAc)2. Antibodies directed against the active site region of hen lysozyme reacted with the affinity labelled enzyme to a much lesser extent than with hen lysozyme. The reversible complex formed between hen lysozyme and (GlcNAc)2 behaved in the assay with the "active site-directed" antibodies in a manner identical to the affinity labelled enzyme, strongly suggesting that in both cases the (GlcNAc)2 occupies the same site on the enzyme (subsites B and C). The "active site-directed" antibodies were used for the comparison of several other lysozymes and of bovine α-lactalbumin to hen egg-white lysozyme. Correlations were found between the immunological reactivity of the proteins tested and the differences in their amino acid sequences, in particular with the sequences presumed to be present in the region of their active site. © 1972.