A partial characterization of polyphenol oxidase (PPO) in papaya fruits is described in this work. Differences among papaya fruits from hermaphrodite and female flowers in terms of PPO activity are also presented. Total soluble PPO activity in female fruits was higher than in hermaphrodite fruits during all ripening proccesses, and greater PPO values were obtained from green papayas. In this ripening stage, female fruits exhibited 30% more PPO activity than hermaphrodite fruits. Specific PPO activity also underwent this evolution. Female green papayas showed a significantly higher PPO activity. This difference became insignificant in ripe fruits (10 days at 14 degrees C). Native PAGE experiments showed the presence of six PPO isoenzymes in hermaphrodite papayas whereas PPO from female fruits separated into only four bands (revealed with 0.003 M gallic acid). Assays of incubation with 0.003 M gallic acid followed by ethanolic washings produced a slightly different PPO pattern (five PPO active bands for hermaphrodite green fruits and four PPO active bands for female green ones). Through ripening, the PPO isoenzyme pattern did not undergo significant changes; only a band (R(f) = 0.28) disappeared in the PPO extracts of mature-green, ripe, and over-ripe hermaphrodite fruits.441030753079