Some characteristics of peroxidase secreted by cotton ovule cultures.

Cotton (Gossypium hirsutum L.) ovule cultures secreted a soluble peroxidase into the surrounding medium, resulting in a 200-fold increase in this activity during the 30-day growth period. The peroxidase activity was thermostable from 4°C to 60°C and displayed a pH optimum of 5.5 to 6.0. The ovule peroxidase was susceptible to periodate treatment and very resistant to protease digestion. The data suggest that the peroxidase activity is a glycoprotein. Interpretation of peroxidase data may be complicated by the presence of phenol oxidase activity in the same preparations. The presence of phenol oxidases was ruled out by the inaction of a tyrosinase-specific inhibitor, tropolone.