Characterization of recombinant fungal phytase (phyA) expressed in tobaccoleaves

The phyA gene from Aspergillus ficuum coding for a 441-amino-acid full-leng th phytase was expressed in Nicotiana tabacum (tobacco) leaves. The express ed phytase was purified to homogeneity using ion-exchange column chromatogr aphy. The purified phytase was characterized biochemically and its kinetic parameters were determined. When the recombinant phytase was compared with its counterpart from Aspergillus ficuum for physical and enzymatic properti es, it was found that catalytically the recombinant protein was indistingui shable from the native phytase. Except for a decrease in molecular mass, th e overexpressed recombinant phytase was virtually the same as the native fu ngal phytase. While the temperature optima of the recombinant protein remai n unchanged, the pH optima shifted from pH 5 to 4. The results are encourag ing enough to open the possibility of overexpressing phyA gene from Aspergi llus ficuum in other crop plants as an alternative means of commercial prod uction of this important enzyme. (C) 1999 Academic Press.