caa a22 4500 46315696X CHVBK 20180406164737.0 cr unu---uuuuu 170326e20071101xx s 000 0 eng 10.1007/s00217-006-0513-8 doi (NATIONALLICENCE)springer-10.1007/s00217-006-0513-8 Partial characterization of lettuce ( Lactuca sativa L.) polyphenol oxidase [Elektronische Daten] [Serap Doğan, Ümran Salman] Polyphenol oxidase (PPO) from garden lettuce (Lactuca sativa L.) was partially purified by ammonium sulphate ((NH4)2SO4) precipitation and dialysis, and then some of its kinetic properties such as optimum pH and temperature, substrate specificity, thermal inactivation and inhibition were investigated. The total phenolic and protein contents of Lactuca sativa L. extracts were determined according to the Folin-Ciocalteu and Bradford methods, and found to be 304mg/100g on a fresh weight basis and 494μg/mL, respectively. PPO activity was determined using 4-methylcatechol, catechol and pyrogallol as substrates. Kinetic parameters, K m and V max, were calculated from Lineweaver-Burk plots. According to V max/K m ratio, pyrogallol was the most suitable substrate, followed by catechol and 4-methylcatechol. The optimum temperature and pH values were 30, 40 and 30°C; and 6.5, 8.0 and 7.5 for 4-methylcatechol, catechol and pyrogallol substrates, respectively. The thermal inactivation of PPO was investigated at 35, 55 and 75°C. The enzyme activity decreased with increasing temperature. The effect of different inhibitors on partially purified Lactuca sativa L. PPO was spectrophotometrically investigated. For this purpose, tropolone, glutathione, ascorbic acid and 4-aminobenzoic acid were used to inhibit the activity of Lactuca sativa L. PPO at different concentrations. From the experimental results, it was found that glutathione was found to be the most potent inhibitor for Lactuca sativa L. PPO. Springer-Verlag, 2006 Lactuca sativa L nationallicence Lettuce nationallicence Polyphenol oxidase nationallicence Substrate specificity nationallicence Optimum pH and temperature nationallicence Inactivation nationallicence Inhibition nationallicence Doğan Serap Department of Biology, Faculty of Science and Literature, Balikesir University, 10145, Balikesir, Turkey aut Salman Ümran Department of Biology, Faculty of Science and Literature, Balikesir University, 10145, Balikesir, Turkey aut European Food Research and Technology Springer-Verlag 226/1-2(2007-11-01), 93-103 1438-2377 226:1-2<93 2007 226 217 https://doi.org/10.1007/s00217-006-0513-8 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00217-006-0513-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Doğan Serap Department of Biology, Faculty of Science and Literature, Balikesir University, 10145, Balikesir, Turkey aut NATIONALLICENCE 700 1- Salman Ümran Department of Biology, Faculty of Science and Literature, Balikesir University, 10145, Balikesir, Turkey aut NATIONALLICENCE 773 0- European Food Research and Technology Springer-Verlag 226/1-2(2007-11-01), 93-103 1438-2377 226:1-2<93 2007 226 217 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer