Title
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First report of urease activity in the novel systemic fungal pathogen Emergomyces africanus : a comparison with the neurotrope Cryptococcus neoformans
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Author
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Abstract
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Cryptococcus neoformans is an opportunistic pathogen responsible for the AIDS-defining illness, cryptococcal meningitis. During the disease process, entry of cryptococcal cells into the brain is facilitated by virulence factors that include urease enzyme activity. A novel species of an Emmonsia-like fungus, recently named Emergomyces africanus, was identified as a cause of disseminated mycosis in HIV-infected persons in South Africa. However, in contrast to C. neoformans, the enzymes produced by this fungus, some of which may be involved in pathogenesis, have not been described. Using a clinical isolate of C. neoformans as a reference, the study aim was to confirm, characterise and quantify urease activity in E. africanus clinical isolates. Urease activity was tested using Christensen's urea agar, after which the presence of a urease gene in the genome of E. africanus was confirmed using gene sequence analysis. Subsequent evaluation of colorimetric enzyme assay data, using Michaelis-Menten enzyme kinetics, revealed similarities between the substrate affinity of the urease enzyme produced by E. africanus (K-m ca. 26.0 mM) and that of C. neoformans (K-m ca. 20.6 mM). However, the addition of 2.5 g/l urea to the culture medium stimulated urease activity of E. africanus, whereas nutrient limitation notably increased cryptococcal urease activity. |
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Language
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English
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Source (journal)
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FEMS yeast research / Federation of European Microbiological Societies. - Amsterdam
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Publication
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Amsterdam
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2017
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ISSN
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1567-1356
[print]
1567-1364
[online]
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DOI
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10.1093/FEMSYR/FOX069
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Volume/pages
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17
:7
(2017)
, 10 p.
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Article Reference
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fox069
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ISI
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000416721200009
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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Full text (open access)
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