Inhibition Kinetics of Agaricus bisporus (J.E. Lange) Imbach Polyphenol Oxidase

This paper reports the inhibition kinetics of mushroom (Agaricus bisporus; J.E. Lange) polyphenol oxidase (PPO) with benzoic acid, sodium azide and sodium fluoride as inhibitors, and pyrocatechol as substrate. Mushroom PPO was significantly inhibited by all of the tested inhibitors. Diphenolase activity of mushroom PPO exhibited the competitive-type inhibition with benzoic acid as an inhibitor; the inhibition constant KI was found to be 0.046 mM. The inhibition by sodium azide was of the mixed-I type, with a KI of 1.39 mM and KIS of 3.12 mM. A partial mixed-type inhibition pattern was obtained with sodium fluoride, with a KI of 148.97 mM and a KIS of 49.19 mM. The IC50 values were estimated to be 0.147, 3.20, and 123.94 mM for benzoic acid, sodium azide, and sodium fluoride, respectively. Furthermore, benzoic acid was the most effective inhibitor because of its low KI value. The results showed that the type of inhibition was dependent upon both the origin of the PPO and on the substrate.