The purification of urease from Aspergillus nidulans

Isolation and characterization of urease from Aspergillus niger

“…K, value was derived from computer-based calculations based on Michaelis-Menten kinetics using LineweaverBurk and Eadie-Hoftstee plots. These values were comparable to other reported values for urease (Creaser & Porter, 1985;Evans et aE., 1991 ;Mackey & Pateman, 1982). Hydroxyurea and N-methylurea (0 to 2 0 m~) were poor alternative substrates for urease.…”

“…The native molecular mass of urease eluted from the S 300 column was estimated at 250000, which is similar to previous findings (Christians et al, 1991 ;Creaser & Porter, 1985;Mobley & Hausinger, 1989). The single protein band of 83 kDa in the final enzyme preparation indicates that the protein could be composed of three identical subunits (Fig.…”

“…nidulans and A . tamarii, which have reported a single species of urease (Creaser & Porter, 1985;Zawada & Sutcliffe, 1981). By contrast, multiple forms of urease have been discovered in other genera (Dunn et al, 1991;Evans et al, 1991).…”

“…This isolation strategy recovered 0.55% of the original activity and achieved a final specific activity of 1341 pmol min-' (mg protein)-'. The specific activity of the final enzyme preparation was twice that of previous purifications for enzymes of Aspergillus nidulans and Aspergillus tamarii (Creaser & Porter, 1985;Mackay & Pateman, 1980, 1982Zawada & Sutcliffe, 1981).…”

“…Purifications of urease are usually initiated with an acetone, ammonium sulphate or ethanol precipitation (Creaser & Porter, 1985;Evans et af., 1991 ;Mahadevan et al, 1977;Rai, 1989). Increasing the NaCl concentration to 2 0 0 m~ in the crude extract prior to DEAE chromatography allowed the retention of all of the urease activity by the column while permitting > 95% of the soluble protein to elute directly through the column.…”