Ureolytic activity of Nitellopsis obtusa (Characeae)

The decomposition of urea by Nitellopsis obtusa from Characeae was investig ated. The intact cells were exposed to the inhibition by two typical urease inhibitors: boric acid and fluoride ion, used as a criterion to define if urease or UAL-ase is responsible for the ureolytic activity of the algae. I t was found that boric acid and fluoride ion are simple competitive and slo w-binding competitive inhibitors of Nitellopsis obtusa enzyme respectively, which is the response characteristic of urease. The inhibition constants e qual to 2.3 and 0.1 mM for boric acid and fluoride ion, when compared to th ose of jack bean urease, indicate that in the observed kinetic behaviour of Nitellopsis obtusa urease partake transport processes taking place in the intact cells.