Romanian Biotechnological Letters Vol. 20, No. 6, 2015 Copyright © ʹͲͳ5 University of Bucharest Printed in Romania. All rights reserved ORIGINAL PAPER Romanian Biotechnological Letters, Vol. 20, No. 6, 2015 10961 Inhibition of Polyphenol Oxidase Purified from Potato (Solanum tuberosum) Received for publication, March 9, 2015 Accepted, August 7, 2015 HATICE AYSUN MERCIMEK*, GULCIHAN GUZELDAG, FILIZ UCAN, KIVILCIM CAKTU GULER, MUHAMMET KARAMAN, RAMAZAN KARAYILAN Department of Moleculer Biology and Genetics, Kilis 7 Aralık University, 79000, Kilis,Turkey. *Address correspondence to: “Kilis 7 Aralık University, The Faculty of Sciences and Letters, Department of Molecular Biology and Genetics, Kilis, Turkey’’ Tel.: +90 348 822 23 50/1452; Fax: +90 348 822 23 51, * Corresponding author: Email: mersimek@hotmail.com Abstract Enzymatic browning reaction caused by polyphenol oxidases (PPOs) due to negative effects on sensorial and nutritional quality of plants, is one of the most important problem in food industry. This study was designed for characterization and purification of PPO from potato and to determine the inhibitory activity of methanolic extracts of Citrus sp., (lemon) Beta vulgaris (red beet) and Capsicum sp. (chili pepper) on PPO. The molecular weight of partial purified PPO, its enzyme activity against catechol substrat and the amount of total protein in sample were determined as 40 kDa, 1340 EU mL -1 and 433 μg mL -1 , respectively. The characteristic peaks of PPO were clearly observed in FTIR spectra. According to spectrophotometric analyses, it was found that PPO activity inhibition by extracts of chili pepper, lemon and red beet was in the rate of 70, 54 and 60%, respectively. Ascorbic acid content of chili pepper was determined as 143.85 mg 100 g -1 . Out of the three extracts, the chili pepper extract was determined to show the maximum anti-browning effect. In various industrial areas such as food industry, health care and medicine to cure skin disorders, extracts of natural vegetables as an alternative to synthetic PPO inhibitors could be used to prevent enzymatic browning reaction. Keywords: Enzymatic browning, polyphenol oxidase, Solanum tuberosum, inhibition, FTIR 1. Introduction Polyphenol oxidase (PPO) known as phenolase, tyrosinase, monophenol, o-diphenol: oxygen oxidoreductase and EC 1.14.18.1, is a member of oxidoreductases (1-4). PPO, is a group of copper enzymes that catalyzes the oxidation of phenolic compounds by two different reactions by using molecular oxygen as a co-substrate: the hydroxylation of monophenols to o- diphenols, (monophenolase or cresolase activity) and the subsequent oxidation of o-diphenols to o-quinones (diphenolase or catecholase activity) that are reddish-brown pigments (1-2, 5-8). This enzyme is widely found in organisms including plant, fungi, animal and bacteria (2). When a plant encounters with cell-damaging treatments such as crushing, cutting and decay, PPO, located in the plastids of plant cells, may contact with certain phenolic substrates, stored in the vacuoles, leading to browning (1-2, 9-10). As a result of this defense