Endosialidases

Stummeyer, K., Dickmanns, A., Muhlenhoff, M., Gerardy-Schahn, R., and Ficner, R. (2005). Crystal structure of the polysialic acid-degrading endosialidase of bacteriophage K1F. Nat. Struct. Mol. Biol. 12, 90-96. 

In a bacteriophage, an a-(2—>8) endosialidase enzyme is found which hydrolyses the internal bonds of this polysialic acid to a high degree of specificity. The cleavage site must be flanked by at least five sialoside residues on the side of the non-reducing end and by three on the other. The recognition site is exceptionally large, as was already observed in the immunochemical reaction. 

The mode of interaction of polysialic acid with its antibodies is unusual as it requires usually a minimum of about 8-10 sialyl residues for interaction [55-57], Similarly, efficient cleavage of polysialic acid by a bacteriophage endosialidase requires a minimum chain length of 8 sialyl residues (Fig. 10) [55,58]. A likely explanation is that the interacting molecules are recognizing a conformational epitope of the polysialic acid chain [59],... 

Endosialidases Versatile Tools for the Study of Polysialic Acid... 

The active endosialidase with its ability to degrade specifically polysialic acid represents a powerful tool for studying the chemistry, metabolism, and biological roles of polysialic acid. The inactive endosialidase, on the other hand, specifically able to recognize and remain bound to polysialic acid, represents a sensitive and convenient tool for the specific detection of polysialic acid in different applications. 

Table 1 Overview of isolated bacteriophages specific for Escherichia coli K1 carrying endosialidase activity...

Name Virus family Host strain or lysogen Phage isolation Endosialidase gene cloned Enzyme... 

Endosialidases (endo-a-sialidase, endo-Af-acetylneuraminidase) cleave within a... 

The first exosialidase was discovered by 1942 [92]. After 35 years, endosialidases were discovered in a bacteriophage lysate to promote research in the field of polysialic acid [35, 93, 94]. Exo-a-sialidase has been listed in the lUBMB nomenclature since 1961, while endo-a-sialidase and anhydrosialidases have been incorporated much later, in 1990 [95] and 1992, respectively. The endo-a-sialidase (EC 3.2.1.129) is aglycosyl hydrolase which cleaves a2,8-linkages of polysialic acid. Names and reactions of sialidases are summarized in Table 2. 

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