Inhibition of Partial purified Polyphenol Oxidase of Solanum Lycopersicum Using L-Cysteine and L-Glycine

L-glycine and L-cysteine exhibit, strong inhibition of partial purified PPO at small cherry Tomate. The concentration of L-glycine inhibiting PPO activity by 50% (IC50) was 0.5 and 0.4 mM at PH 6.7 and 8, respectively. The inhibition of partial purified PPO activity is PH and inhibitor dependent. Kinetic studies indicate that L-glycine is a uncompetitive inhibitor and L-cysteine is competitive and noncompetitive inhibitor of PPO activity. Vmax and Km for pyrogallol oxidation at PH 6.7 and in presence of L-glycine (1.4M) was 0.09 ?A min-1 and 10 mM. Vmax for pyrogallol oxidation at PH 8 and in absence of L-glycine was 0.09 ?A min–1, with a Km of 3.5 mM. Kinetics parameters indicated the highest catalytic efficiency ( units mg–1 prot mM–1) with pyrogallol and L-glycine at PH 8: 4 , then with L-cystein at PH 8: 1.7, L-glycine at PH 6.7: 1.4 and L-cystein at PH 6.7: 0.25.