Purification and characterization of polyphenol oxidase from cauliflower (Brassica oleracea L.)

J Agric Food Chem. 2012 Apr 11;60(14):3673-8. doi: 10.1021/jf300380b. Epub 2012 Apr 3.

Abstract

Polyphenol oxidase (PPO) of cauliflower was purified to 282-fold with a recovery rate of 8.1%, using phloroglucinol as a substrate. The enzyme appeared as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The estimated molecular weight of the enzyme was 60 and 54 kDa by SDS-PAGE and gel filtration, respectively. The purified enzyme, called phloroglucinol oxidase (PhO), oxidized phloroglucinol (K(m) = 3.3 mM) and phloroglucinolcarboxylic acid. The enzyme also had peroxidase (POD) activity. At the final step, the activity of purified cauliflower POD was 110-fold with a recovery rate of 3.2%. The PhO and POD showed the highest activity at pH 8.0 and 4.0 and were stable in the pH range of 3.0-11.0 and 5.0-8.0 at 5 °C for 20 h, respectively. The optimum temperature was 55 °C for PhO and 20 °C for POD. The most effective inhibitor for PhO was sodium diethyldithiocarbamate at 10 mM (IC(50) = 0.64 and K(i) = 0.15 mM), and the most effective inhibitor for POD was potassium cyanide at 1.0 mM (IC(50) = 0.03 and K(i) = 29 μM).

MeSH terms

  • Brassica / enzymology*
  • Catechol Oxidase / chemistry*
  • Catechol Oxidase / isolation & purification*
  • Catechol Oxidase / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme Stability
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Molecular Weight
  • Oxidation-Reduction
  • Phloroglucinol / metabolism
  • Substrate Specificity

Substances

  • Phloroglucinol
  • Catechol Oxidase