Akademik Veri Yönetim Sistemi
JOURNAL OF ENZYME INHIBITION AND MEDICINAL CHEMISTRY, cilt.20, sa.3, ss.297-302, 2005 (SCI-Expanded)
Polyphenol oxidase (PPO) of nettle (Urtica dioica L.) was extracted and purified through (NH4)(2)SO4 precipitation, dialysis, and CM-Sephadex ion-exchange chromatography and was used for its characterization. The PPO showed activity to catechol, 4-methylcatechol, L-3,4-dihydroxyphenylalanine (L-DOPA), L-tyrosine, p-cresol, pyrogallol, catechin and trans-cinnamic acid. For each of these eight substrates, optimum conditions such as pH and temperature were determined and L-tyrosine was found to be one of the most suitable substrates. Optimum pH and temperature were found at pH 4.5 and 30 degrees C respectively and K-m and V-max values were 7.90 X 10(-4) M, and 11290 EU/mL for with L-tyrosine as substrate. The inhibitory effect of several inhibitors, L-cysteine chloride, sodium azide, sodium cyanide, benzoic acid, salicylic acid, L-ascorbic acid, glutathione, thiourea, sodium diethyl dithiocarbamate, beta-mercaptoethanol and sodium metabisulfite were tested. The most effective was found to be sodium diethyl dithiocarbamate which acted as a competitive inhibitor with a K-i value of 1.79 X 10(-9) M. In addition one isoenzyme of PPO was detected by native polacrylamide slab gel electrophoresis.