A number of literatures reported that PPO activity could be regulated
by the action of glutathioneshows the effect of different concentrations
of glutathione on the PPO activity from grape juice.
Glutathione maximally inhibited PPO activity by 99.4% at a concentration
of 0.04% (Fig. 1), and therefore, 0.04% of glutathione was
used for further study. In contrast to our results, several previous
reports indicated that the optimal glutathione concentration for
PPO inhibition were 10 mmol litre1 (approximately 0.31%),
0.06%, and 0.08%, respectivelyThe different optimum glutathione concentration reported
may be related to enzyme source.