BIOCHEMICAL-PROPERTIES OF A NEURAMINIDASE OF TRICHOMONAS-VAGINALIS

Trichomonas vaginalis possesses a membrane-associated neuraminidase ac tivity that is released into culture medium during its growth in vitro . The neuraminidase shows an optimum pH of 4.5 and a K-m, of 0.15 mM f or (4-methylumbelliferyl)-alpha-D-N-acetyl-neuraminic acid as a substr ate. This enzyme releases mainly alpha-2,3-linked sialic acid because it is able to liberate sialic acid from sialyllactose (mainly (alpha-2 ,3) but not from mucin (alpha-2,6) or fixed erythrocytes (mainly alpha -2,6). The neuraminidase activity is strongly inhibited by 2,3-dehydro -2-deoxy-N-acetyl neuraminic acid, whereas EGTA and Ca2+ do not affect the activity. Gel filtration-fast protein liquid chromatography of cu lture supernatant displays a single peak of neuraminidase activity wit h molecular weight 52,000. The levels of neuraminidase activity are va riable in fresh and long-term grown isolates of T. vaginalis, regardle ss of time in culture. However, there are 2 kinds of isolates, 1 group with high neuraminidase activity and able to secrete the enzyme durin g growth and the other with low neuraminidase activity. The results su ggest that T. vaginalis possesses a membrane-associated neuraminidase that is present to a variable degree in different isolates.