Phenol oxidase activity in the integument of the silkworm Bombyx mori infected with Beauveria bassiana and Spicaria fumoso-rosea

Abstract

Phenol oxidase activity reflected by the oxidation of cresol, catechol, and DOPA was investigated by use of the conventional Warburg manometric method in the integument of silkworm larvae ( Bombyx mori) inoculated with Beauveria bassiana and Spicaria fumoso-rosea. In fungus-inoculated larvae, the activity of phenol oxidase was determined separately for larvae with blackened integumentary spots and for those with no spots. Similar results were obtained with the oxidation of all three substrates. The oxidase activity in the integument of infected larvae decreased during the advanced stages of the disease, especially immediately before death. The activity was lower in the integuments of larvae infected with B. bassiana than in those infected with S. fumoso-rosea. The activity in the integuments of nonblackened larvae decreased with time when compared to that of blackened larvae. This was the case for each fungus. The decrease in enzyme activity was most striking in the oxidation of cresol.