title: Phytase activity in Cryptococcus laurentii ABO 510.
abstract: Ten Cryptococcus strains were screened for phytase activity, of which the Cryptococcus laurentii ABO 510 strain showed the highest level of activity. The cell wall-associated enzyme displayed temperature and pH optima of 62 degrees C and 5.0, respectively. The enzyme was thermostable at 70 degrees C, with a loss of 40% of its original activity after 3 h. The enzyme was active on a broad range of substrates, including ATP, D-glucose 6-phosphate, D-fructose 1,6-diphosphate and p-nitrophenyl phosphate (p-NPP), but its preferred substrate was phytic acid (K(m) of 21 microM). The enzyme activity was completely inhibited by 0.5 mM inorganic phosphate or 5 mM phytic acid, and moderately inhibited in the presence of Hg(2+), Zn(2+), Cd(2+) and Ca(2+). These characteristics suggest that the Cry. laurentii ABO 510 phytase may be considered for application as an animal feed additive to assist in the hydrolysis of phytate complexes to improve the bioavailability of phosphorus in plant feedstuff.
authors.affiliation: Department of Microbiology, Stellenbosch University, Matieland, South Africa.
authors.forename: Jason
authors.initials: J
authors.lastname: van Staden
authors.forename: Riaan
authors.initials: R
authors.lastname: den Haan
authors.forename: Willem H
authors.initials: WH
authors.lastname: van Zyl
authors.forename: Alfred
authors.initials: A
authors.lastname: Botha
authors.forename: Marinda
authors.initials: M
authors.lastname: Viljoen-Bloom
mesh_terms: D010832:6-Phytase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000821:Animal Feed; D002473:Cell Wall / Q000201:enzymology; D003454:Cryptococcus / Q000201:enzymology* / Q000378:metabolism; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D010833:Phytic Acid / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D019216:Metals, Heavy; D010710:Phosphates; D010833:Phytic Acid; D010832:6-Phytase