Study of oxidation catechol by potato polyphenoloxidase (PFO) inhibited by kluwek fractions and bht: The enzymatic browning reaction of fruits and vegetables are catalysed by polyphenoloxidase(PFO) .Study was carried out to observe the PFO optimal activity condition and the inhibition effect of kluwek fraction (Pangium edule reinw fractions) and bht. The optimum inhibition was observed in addition of 0.05 % fraction A (neutral),0.05% fraction B(weak acid) and 0.10% fraction C(strong acid) that decreased the formation of quinon by 66.29 %.49.59% and 55.62% respectively. The inhibition activity is bht>A>c>b and it's totally different with the inhibition not only determined by the kind of inhibitor but meanly the kind of enzymaticc reaction(enzyme and substrate)