Cloning of the gene coding for phytase(phytA) from Aspergillus ficuum NRRL3135 and detection of its function

The gene coding for extracellular, glycosylated phytase(phytA) from Aspergillus ficuum NRRL3135 was cloned partially (active domain), without its intron and SP coding region. After being inserted into a S cerevisiae high-efficiency expression vector YFD59, under control of PGK constitutive promotor and ADH1 terminator, the manipulated phytA gene fragment merged with the 3'end of a - factor coding sequence correctly for translation, which had been comfirmed by DNA sequencing. Then the S.cerevisiae host BJ1991 was transformed with the recombinant expression vector by the method of Lithium Acetate. Yeast transformants were selected by URA3 selection, then cultured in YNB medium. Phytase activity was detected, revealing the expression product could be secreted efficiently with normal biological founction ( nearly 12 fold of that of the wt BJ1991). Compared with wild-type PhytA, the expression product posses similar pH adaptability, however lower temperature resistance.