Two peroxidases, cPOD-I and rPOD-II, have been isolated and purified from cotton cell suspension and their biochemical characteristics studied. rPOD-II from R405-2000, a non-embryogenic cultivar, has higher activity than cPOD-I derived from Coker 312, which developed an embryogenic structure. The cPOD-I and rPOD-II had molecular mass of 39.1 and 64 kDa respectively, as determined by SDS-PAGE. Both enzymes showed high efficiency of interaction with the guaiacol at 25 mM. The optimal pH for cPOD-I and rPOD-II activity was 5.0 and 6.0, respectively. The enzyme had an optimum temperature of 25 degrees C and was relatively stable at 20-30 degrees C. The isoenzymes were highly inhibited by ascorbic acid, dithiothreitol, sodium metabisulfite, and beta-mercaptoethanol. Their activities were highly enhanced by Al3+, Fe3+, Ca2+, and Ni2+, but they were moderately inhibited by Mn2+ and K+. The enzyme lost 50% to 62% of its activity in the presence of Zn2+ and Hg2+.