Sialidase Salmonella typhimurium

Scheme 9.11 Enzymatic transsialylation of four MPEG-DOXyl glycosides with sialidases from Vibrio cholerae and Salmonella typhimurium. V. cholerae sialylated in position 6 of the terminal monosaccharide units with yields of 12-17%, whereas S. typhimurium sialylated position 3 of the same monosaccharide units (yields 14-24%).

Seven different bacterial sialidases, including six commercially available sialidases from Arthrobacter ureafaciens, Clostridium perfingens. Streptococcus sp. IID, Vibrio cholera. Salmonella typhimurium, and Streptococcus pneumoniae, as well as PmSTl which also possesses sialidase activity (20), were used as model systems to test the application of the sialoside library and the 96-well plate based high-throughput colorimetric screening method. 

With regard to the primary reaction product. Salmonella typhimurium sialidase behaves quite differently, since it was reported not to retain the configuration of sialic acid during the hydrolysis of Neu5Ac /7-nitrophenyl a-glycoside. As primary reaction product the P-isomer was detected by optical rotation measurements [759,760]. 

In the first primary structures of microbial sialidases, obtained by cloning and sequencing of the respective genes from Clostridium perfringens [769], Vibrio cholerae [770], Clostridium sordellii [77 ] and Salmonella typhimurium [772], an amino acid sequence motif was detected, which is repeated four-fold in each protein S-X-D-X-G-X-T-W [773]. This motif, named the Asp-box, was found in all 16 sialidases of animals, trypanosomes, and bacteria, which have so far been sequenced (see refs. [660,768] and Table 18). In viral sialidases, however, the motif was rarely detectable (e.g. only the sialidase from N9 influenza A virus strain exhibits the complete motif [786] and has probably undergone mutational alterations). 

Fig. 17. Three-dimensional structure of Salmonella typhimurium LT2 sialidase with bound inhibitor Neu2en5Ac obtained from X-ray crystallography. From ref. [790] by permission of National Academy of Sciences, New York.

Fig. 18. Amino acids essential for bacterial sialidase action. The positions of the amino acid residues interacting with different parts of the Neu5Ac molecule or forming a hydrophobic pocket (by Leu, Trp and Met indicated by a dotted line at the left side of the sialic acid molecule) are shown. Vc, Vibrio cholerae sialidase [791] St, Salmonella typhimurium sialidase [790] and Cp, Clostridium perfringens sialidase [R.G. Kleineidam, personal communication].

Crennell SJ, Garman EF, Laver WG, Vimr ER, Taylor GL (1993) Crystal structine of a bacterial sialidase (from Salmonella typhimurium LT2) shows the same fold as an influenza virus neuraminidase. Proc Natl Acad Sci USA 90 9852-9856... 

The crystal structures of two representative small sialidases, with molecular weights around 40 kDa, have been determined one from Salmonella typhimurium [17] and one from Micromonospora viridifaciens [I8j. These reveal the same P-propeller fold seen in the influenza virus neuraminidase (Figure 2), despite having no sequence similarity to the viral enzyme, and not containing any disulphide bonds in contrast to the seven conserved disulfides in the viral enzyme. 

L.L. Hoyer, P. Roggentin, R. Schauer and E.R. Vimr, Purification and properties of cloned Salmonella typhimurium LT2 sialidase with virus-typical kinetic preference for sialyl a 2,3 linkages. J. Biochem. (Tokyo), 1991, llO, 462-467. 

Hoyer, L. L., Hamilton, A. C., Steenbergen, S. M., and Vimr, E. R., 1992, Cloning, sequencing and distribution of the Salmonella typhimurium LT-2 sialidase gene, nanH, provides evidence for interspecies gene transfer. Mol. Microbiol. 6 873-884. 

Salmonella typhimurium LT2 sialidase with virus-typical kinetic preference for sialyl a2-3 linkages, J. Biochem. 110 462-467. 

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