BINDING OF COPPER AND ZINC IONS BY AMINOACYLASE FROM ASPERGILLUS-ORYZAE

The metal-binding properties of the aminoacylase from Aspergillus oryzae were investigated by methods of intrinsic tryptophan fluorescence and differential scanning microcalorimetry. At netral pH values the enzyme cooperatively binds three to four Cu2+ ions per molecule with association constant (2-9) . 10(5) M-1. Evidently Zn2+ ions are bound at the same sites. Possibly histidine residues are present in certain binding sites. The binding of Cu2+ and Zn2+ ions increases the stability of the enzyme to the action of acidic and alkaline pH but decreases its thermal stability.