Pear polyphenol oxidase (PPO) has been isolated by using two sequentia
l phase partitionings with Triton X-114 (TX-114), The enzyme showed mo
nophenolase activity when assayed on p-hydroxyphenyl propionic acid (P
HPPA) with 3-methyl-2-benzothiazolinone hydrazone (MBTH) in a continuo
us 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 enzym
e 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