[Role of metal ions in the catalytic activity of Aspergillus oryzae aminopeptidase].

The paper deals with the role of metals in the catalytic action of Asp. oryzae aminopeptidase. Cobalt ions are more specific activators than Mn2+ and Mn2+ and evoke its maximal activity. Sinergic activation of Co2+ in combination with Mn2+ and Mg2+ was not found in contrast to some aminopeptidases of animal origin. Activation of the enzyme with cobalt chloride depends on temperature. By the 10th minute of incubation the activation reaches its maximum: 650 and 900% at 20 and 40 degrees C, respectively. EDTA (10(-2) M) inactivates completely aminopeptidase for 3h; this process is intensified in the presence of leucine (10(-3) M). Aminopeptidase is also inactivated by chelating agents, such as o-phenantroline and 2,2'-dipyridyl. When the temperature rises from 20 to 40 degrees C the intensification of these reagents effect is insignificant. Cobalt ions reduce and activate to some extent the enzyme after inhibition with EDTA.