title: Polyphenol oxidases from latex of Hevea brasiliensis: purification and characterization.
abstract: Polyphenol oxidase (PPO) was isolated from the B-serum obtained after repetitive freeze-thawing of the bottom fraction isolated from ultracentrifuged fresh latex. The B-serum was subjected to acetone precipitation and CM-Sepharose chromatography, affording two PPOs, PPO-I and PPO-II, which, upon SDS-PAGE, were 32 and 34 kDa, respectively. Both PPOs possessed the same pI (9.2), optimum pH (7) and optimum temperature (35-45 degrees C). They are stable up to 60 degrees C and active at broad pH ranges from 4-9. The K(m) values of PPO-I for dopamine, L-dopa and catechol as substrates are 2.08, 8.33 and 9.09 mM, while those for PPO-II are 2.12, 4.76 and 7.14 mM, respectively. Among various PPO inhibitors tested, 4-hexylresorcinol was the most potent. Anionic detergents were among the most effective activators of the enzymes, while cationic and nonionic detergents showed little and no effect on the PPO activities, respectively.
authors.affiliation: Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
authors.forename: Dhirayos
authors.initials: D
authors.lastname: Wititsuwannakul
authors.forename: Nopphakaew
authors.initials: N
authors.lastname: Chareonthiphakorn
authors.forename: Mario
authors.initials: M
authors.lastname: Pace
authors.forename: Rapepun
authors.initials: R
authors.lastname: Wititsuwannakul
mesh_terms: D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D028482:Hevea / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007840:Latex / Q000737:chemistry*; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D004791:Enzyme Inhibitors; D007840:Latex; D004156:Catechol Oxidase