Some characteristics of active and latent monophenolase of mushroom polyphenol oxidase

Latent form of monophenolase of mushroom polyphenol oxidase (PPO) was activated by 0,1% sodium dodecyl sulfate (SDS). The addition of increasing concentrations of 4-methylcatechol di minished lag period of active and total monophenolase activity, measured using p-cresol with L-proline as a substrate. Changes of lag period were described by equation of one phase exponential decay when concentration of substrate varied from l to 10 mM. Affinity ( 1/Km) toward substrate of latent monophenolase was over two times higher than that of the active form, while the maximum velocity (Vmax) was two times lower. The catalytic power (Vmax/Km) of both forms of monophenolase were almost equal. Electrophoretic analysis followed by scanning technique of the gels was used. Absorbancy of spots, determined from computer image of isoenzyme bands pattern allowed for qualitative and quantitative estimation of electrophoregrams. Presence of one additional clearly defined slow migrating isoenzyme for SDS activated monophenolase differed in this respect active (2 bands) and total (3 bands) forms of monophenolase