Abstract
Cell-free extracts of a selection of yeasts were analysed for urease activity. Species in the genera Filobasidiella, Rhodotorula and Rhodosporidium had the highest specific activities. Immune inactivation experiments showed widely different degrees of cross-reactivity between antiserum to jack bean urease and yeast ureases, with Rhodosporidium paludigenum (71%) the most and Schizosaccharomyces pombe (3%) the least affected. Only R. paludigenum urease was detected with anti-jack bean urease antiserum on Western blots. The urease of Rhodosporidium paludigenum was partially purified by column chromatography. The native enzyme was found to have a subunit size of 72 +/- 7 kDa probably in an octamer arrangement of 560 +/- 8 kDa, having a specific activity of 62.5 mumol urea hydrolysed min-1 (mg protein)-1. The enzyme was stable in the pH range 5-11 with optimum activity at pH 7.8. Vmax and Km values were determined as 65.2 +/- 3.8 mumol min-1 (mg protein)-1 and 3.81 +/- 0.47 mM, respectively.
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