The overall objective of this work is to describe in detail the structure-function biochemistry of bacterial neuraminidases. The immediate goal is to investigate the mechanism of action of the homogeneous neuraminidase derived from Arthrobacter sialophilus. Site-directing irreversible inhibitors and transition-state affinity labels prepared from derivatives of 2-deoxy-2,3-dehydro-N-acetylneuraminic acid methyl ester will be used to identify amino acid residues at the active site of the enzyme. The latter compounds may have potential chemotherapeutic value for the treatment of such infectious diseases as influenza and bacterial pneumonia. The preparation of a large, active fragment obtained by proteolysis of the parental enzyme was carried out and its biochemical properties will be determined and compared to those previously obtained for the native enzyme.