Inhibition types and some kinetic properties of tyrosinase of deepwater pink shrimp (Parapenaeus longirostris) from edremit bay

Abstract

Phenoloxidases (POs) are a family of enzymes including tyrosin-ases, catecholases and laccases, which play an important role inimmune defence mechanisms in various invertebrates. The aim ofthis study was to identify the tyrosinase activity present in theextract of deepwater pink shrimp (Parapenaeus longirostris(Lucas, 1846)) at Edremit Bay, (Eaegen Sea) by using as a sub-strate (L-Dopa) and different tyrosinase inhibitors(gallic acid andL-cisteine). Further characterisation was carried out in extractspartly purified using 40–70% ammonium sulfate fractionation.The enzyme had the highest activity at pH 4.0, and the optimumtemperature values of shrimp tyrosinase for L-Dopa found to be35°C. The inhibitory effect of gallic acid and L-cysteine on tyros-inase from deepwater pink shrimp were investigated. Gallic acidand L-cysteine inhibited the oxidation of 3-(3,4-dihydroxylphe-nyl)-L-alanine (L-DOPA) catalyzed by deepwater pink shrimptyrosinase. Gallic acid showed mixed type inhibition with Ki andKi’ values of 8 and 2 mM respectively. L-Cisteine compoundshowed uncompatitive inhibition with Ki’ value of 5.3 mM.