Biochemical characteristics and thermal inhibition kinetics of polyphenol oxidase extracted from Thompson seedless grape

Yongju Zheng, Junling Shi, Zhongli Pan

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Polyphenol oxidase (PPO) was isolated from Thompson seedless grape (Vitis vinifera 'Thompson Seedless'), and its biochemical characteristics were studied. The PPO showed activity to catechol and D, L-DOPA, but not towards monophenol l-Tyrosine, diphenols guaiacol and caffeic acid, and triphenols pyrogallic acid and gallic acid. Apparent Michaelis-Menten constant (K m) and maximum velocity of the reaction (V max) values were 45. 0 ± 0. 05 mM and 500. 0 ± 15. 3 OD 400 nm/min for catechol, and 34. 6 ± 0. 03 mM and 384. 6 ± 11. 7 OD 478 nm/min for D, L-DOPA, respectively. The obtained similar specificity values of V max/K m ratio of catechol and D, L-DOPA indicated their similar affinity to Thompson seedless PPO. The most effective inhibitor was l-cysteine, followed in decreasing order by ascorbic acid, sodium metabisulfite, EDTA, NaCl, and citric acid. It was discovered that metal ions of Mg 2+ and Cu 2+ increased, while Zn 2+ and K + reduced the PPO activity. Sugars showed inhibition on the PPO activity, with higher effect by sucrose and lower effect by fructose and glucose. Optimum pH and temperature for grape PPO activity were 6. 0 and 25 °C with 10 mM catechol as substrate. The enzyme was heat stable between 10 and 25 °C, but showed significant activity loss at temperatures higher than 40 °C and completely inactivation at 70 °C for 10 min. Thermal inactivation of PPO showed a first-order kinetic with an activation energy (E a) of 146. 1 ± 10. 8 kJ/mol at pH 6. 0.

Original languageEnglish
Pages (from-to)607-616
Number of pages10
JournalEuropean Food Research and Technology
Volume234
Issue number4
DOIs
StatePublished - Apr 2012
Externally publishedYes

Keywords

  • Biochemical characteristics
  • Polyphenol oxidase
  • Thermal inhibition kinetic
  • Thompson seedless
  • Vitis vinifera

Fingerprint

Dive into the research topics of 'Biochemical characteristics and thermal inhibition kinetics of polyphenol oxidase extracted from Thompson seedless grape'. Together they form a unique fingerprint.

Cite this