12 Neuraminidases

Abstract

Neuraminidases are widely distributed in microorganisms and animal tissues. Viruses, bacteria, and avian and mammalian tissues are known to possess neuraminidase activity. Bacterial neuraminidases from Vibrio cholerae , Diplococcus pneumoniae , Clostridium perfringens , and Streptococcus are generally found in the culture medium. In other bacteria, neuraminidase has been shown to be part of the cell, as in Corynebacterium diphtheriae . Neuraminidase is also found in many tissues and organs of mammals, though the activity is lower when compared with that of viral and bacterial neuraminidases. Besides the viral, bacterial, and mammalian neuraminidases, this enzyme is also reported to be present in the chorioallantoic membrane of the chick embryo. The best sources of the enzyme are the influenza virus particle and Vibrio cholerae . In the virus, the enzyme is a built-in constituent of the mosaic structure of the particle surface; in contrast, V. cholerae , during its growth under suitable conditions, produces and releases the enzyme into the culture medium. The first inhibitor of neuraminidase activity to be found was N -acetyl-neuraminic acid. Another group of potent neuraminidase inhibitors are N -substituted oxamic acids. The most active inhibitors for both influenza A 2 Singapore neuraminidase and Vibrio cholerae neuraminidase are N -phenyloxamic acid, N -(2-pyridyl)oxamic acid, N -(2-thiazolyl)oxamic acid, and thiooxamilic acid. The assay method for neuraminidase depends on the substrate used. The most commonly used substrate in neuraminidase work is N -acetylneuraminosyl (α,2→3) lactose.