Activation of polyphenol oxidase by polyamines.
Latent polyphenol oxidase was extracted and partially purified from grape cell suspension cultures. The enzyme was shown to be activated by polyamines. Activation of the enzyme increased with increasing polyamine concentrations and half-maximal activation was in the order of 8mM. Kinetic parameters, Km and Vm, were also calculated for the latent and activated enzymes. The activating effect of polyamines was studied at different pH values. Optimum pH was 4.5 for latent and activated enzymes. However, the highest degree of activation was obtained at pH 5. Activation caused a higher sensitivity of polyphenol oxidase to pH and temperature. The ability of polyamines to activate the enzyme may suggest a limited conformational change.
Jiménez-Atiénzar
M
M
Departamento de Bioquímica, Facultad de Veterinaria, Universidad de Murcia, Spain.
Angeles Pedreño
M
M
García-Carmona
F
F
D004156:Catechol Oxidase / Q000378:metabolism*; D002478:Cells, Cultured; D003959:Diamines / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005638:Fruit; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010940:Plant Proteins / Q000378:metabolism*; D011073:Polyamines / Q000494:pharmacology*; D011487:Protein Conformation; D013696:Temperature
D003959:Diamines; D010940:Plant Proteins; D011073:Polyamines; D004156:Catechol Oxidase