FIG. 1.

Effect of chemical modification on the pH activity profile of A. fumigatus Q27L phytase. The surface carboxy groups of A. fumigatus Q27L phytase were glycinamidylated as described in Materials and Methods. Subsequently, one aliquot of the modified enzyme was treated with hydroxylamine in order to regenerate modified Tyr residues, while the other aliquot was not. Chemical modification, independently of hydroxylamine treatment, caused 70 to 75% inactivation of the enzyme (measured at pH 5.0). Symbols: ▪, nonmodified; •, modified and hydroxylamine treated; ▵, modified but not exposed to hydroxylamine treatment.