THE SPECIFICITY OF VIRAL SIALIDASES - THE USE OF OLIGOSACCHARIDE SUBSTRATES TO PROBE ENZYMIC CHARACTERISTICS AND STRAIN-SPECIFIC DIFFERENCES

Google Scholar
  • 1 January 1982
    • journal article
    • research article
    • Vol. 124  (3) , 521-525
Abstract
The action of sialidases from Newcastle disease virus (NDV), influenza A2 virus (IA2V) and fowl plague virus (FPV) on sialyloligosaccharide substrates containing .alpha.2.sbd.3, .alpha.2.sbd.6 or .alpha.2.sbd.8 linkages was studied. In all cases 2.sbd.3-linked sialic acids were preferentially released. Compared with II6Neu5AcLac, all 2.sbd.6-linked substrates, including sialyl-N-acetyllactosamine and its asparaginyl derivative, a urinary hexasaccharide and Neu5Ac(2.sbd.6)GalNAc were cleaved at improved rates by NDV and less by FPV sialidases. In the case of IA2V sialidase the asparaginyl oligosaccharide was very poorly cleaved, illustrating a variation in viral strain specificity. A decrease in relative rates was observed in the order NDV > IA2V > FPV for substrates with 2.sbd.3 linkages relative to II6Neu5AcLac. The greatest relative rate was 470-fold higher. The 2.sbd.3-linked sialyl-N-acetyllactosaminylasparagine and IV3Neu5AcLcOse4 were poor substrates for the IA2V sialidase, but the rates were greater than with the 2.sbd.6-linked substrates. The ganglioside substrate II3Neu5AcLacCer showed lower activity than its oligosaccharide analog, but neither II3Neu5AcGgOse4Cer not its oligosaccharide were substrates. The Km values for 2.sbd.6-linked substrates were generally of the order 10 mM while those for the 2.sbd.3-linked substrates were .apprx. 1 mM. The V values were consistently higher for the 2.sbd.3-linked substrates. IV3Neu5AcLcOse4 showed high Km and very high V values, while the 2.sbd.8-linked disialyllactose showed this trend only with NDV enzyme, the IA2V and FPV sialidases exhibiting high Km and low V values. The results are discussed in the light of the current knowledge of viral sialidase specificity and relative to the binding of virus particles to cell surfaces.