Evidence for a common regulation in the activation of a polyphenol oxidase by trypsin and sodium dodecyl sulfate.
Polyphenol oxidase (PPO) was extracted from beet root, in both soluble and membrane fractions, and in both cases the enzyme was in a latent state. PPO from the membrane fraction showed no diphenolase activity unless it was activated by trypsin or sodium dodecyl sulfate (SDS). The kinetics of the activation process of latent PPO by trypsin was studied and the specific rate constant of active PPO formation, k 3 , showed a value of 0.03 s(-1). The protease-activated form showed a pH optimum (6.5) and kinetic properties identical to those of the SDS-activated enzyme. Evidence is provided for the existence of a common peptide responsible for the regulation of the activity of the enzyme by both proteolysis and SDS detergent. Formation of the active proteolyzate was followed by spectroscopic measurements, Western blotting and partially denaturing SDS-PAGE.
Gandía-Herrero
Fernando
F
Departamento de Bioquímica y Biología Molecular A, Unidad Docente de Biología, Facultad de Veterinaria, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain.
Jiménez-Atiénzar
Mercedes
M
Cabanes
Juana
J
García-Carmona
Francisco
F
Escribano
Josefa
J
D027461:Beta vulgaris / Q000201:enzymology*; D015153:Blotting, Western; D004156:Catechol Oxidase / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018517:Plant Roots / Q000201:enzymology; D012967:Sodium Dodecyl Sulfate; D014357:Trypsin / Q000494:pharmacology*
D012967:Sodium Dodecyl Sulfate; D004156:Catechol Oxidase; D014357:Trypsin