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BioMed Research International
Volume 2013 (2013), Article ID 540239, 7 pages
http://dx.doi.org/10.1155/2013/540239
Research Article

A Phytase Characterized by Relatively High pH Tolerance and Thermostability from the Shiitake Mushroom Lentinus edodes

1College of Biosciences and Biotechnology, Beijing University of Agriculture, Beijing 102206, China
2State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
3School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong

Received 25 November 2012; Revised 31 January 2013; Accepted 25 February 2013

Academic Editor: Chiu-Chung Young

Copyright © 2013 Guo-Qing Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A monomeric phytase with a molecular mass of 14 kDa was acquired from fresh fruiting bodies of the shiitake mushroom Lentinus edodes. The isolation procedure involved chromatography on DEAE-cellulose, CM-cellulose, Q-Sepharose, Affi-gel blue gel, and a final fast protein liquid chromatography-gel filtration on Superdex 75. The purified phytase demonstrated the unique N-terminal amino acid sequence DPKRTDQVN, which exhibited no sequence similarity with those of other phytases previously reported. It expressed its maximal activity at pH 5.0 and 37°C. Phytase activity manifested less than 20% change in activity over the pH range of 3.0–9.0, considerable thermostability with more than 60% residual activity at 70°C, and about 40% residual activity at 95°C. It displayed a wide substrate specificity on a variety of phosphorylated compounds with the following ranking: ATP > fructose-6-phosphate > AMP > glucose-6-phosphate > ADP > sodium phytate > β-glycerophosphate. The phytase activity was moderately stimulated by Ca2+, but inhibited by Al3+, Mn2+, Zn2+, and Cu2+ at a tested concentration of 5 mM.