Monophenolase activity of polyphenol oxidase from Blanquilla pear

Pear polyphenol oxidase (PPO) has been isolated by using two sequential phase partitionings with Triton X-114 (TX-114), The enzyme showed monophenolase activity when assayed on p-hydroxyphenyl propionic acid (PHPPA) with 3-methyl-2-benzothiazolinone hydrazone (MBTH) in a continuous spectrophotometric method, with high sensitivity and precision. The initial monophenolase activity showed a lag period (tau) prior to the attainment of the steady state rate (V-ss). Both kinetic parameters, V-ss and tau, depended on the enzyme and monophenol concentrations, as well as on the presence of catalytic amounts of o-diphenol. The enzyme showed an optimum pH of 4.3 and the value of K-m toward PHPPA was 0.5 mM. Copyright (C) 1996 Elsevier Science Ltd