title: A survey of yeast ureases and characterisation of partially purified Rhodosporidium paludigenum urease.
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.
authors.affiliation: Department of Microbiology and Biochemistry, University of the Orange Free State, Bloemfontein, Republic of South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Phillips
authors.forename: G H
authors.initials: GH
authors.lastname: Pretorius
authors.forename: P J
authors.initials: PJ
authors.lastname: Du Toit
mesh_terms: D001487:Basidiomycota / Q000201:enzymology*; D015153:Blotting, Western; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D014510:Urease / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D015003:Yeasts / Q000201:enzymology*
chemical_list: D014510:Urease