Browsing by Author "Akkanli, G"

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    Partial purification and characterisation of polyphenol oxidase from celery root (Apium graveolens L.) and the investigation of the effects on the enzyme activity of some inhibitors
    Aydemir, T; Akkanli, G
    Polyphenol oxidase (PPO) of celery root was extracted and partially purified by (NH4)(2)SO4 fractionation and dialysis. Optimum pH and temperature were found at pH 7.0 and 30 degrees C, and K-m and V-max values were 29 mm and 5560 U mL(-1) min(-1) with catechol, respectively. The activation energy of the enzyme with catechol was 17.9 kJ mol(-1) at pH 7.0. In electrophoretic seperation, six isoenzymes were detected with DL-dopa substrate. PPO showed activity to catechol, 4-methylcatechol, pyrogallol, gallic acid, DL-dopa. l-Tyrosine was also tested but was not oxidised by celery root PPO. beta-Mercaptoethanol was found to be the most effective inhibitor. (NH4)(2)SO4, NaCl, KCl and sucrose appeared to be protective agents of celery root PPO against thermal denaturation. Metal ions (Cu2+, Zn2+, Mn2+) were poor inhibitors of the celery root PPO at 1 mm. PPO activity was also inhibited by CaCl2, NaCl, BaCl2, FeSO4 and NiCl2.