| Abstract
| - Salsolinol, a tethrahydroisoquinoline present in banana and biosynthesized from dopamine, wasoxidized by banana pulp polyphenol oxidase to its corresponding salsolinol-o-quinone. This oxidationwas pH-dependent and showed a maximum at acidic pH values. At physiological pH of 5.0, thevalues obtained for the kinetic parameter (Vm and Km) were 62.5 μM/min and 1.7 mM, respectively.When dopamine was added to the reaction medium to imitate physiological conditions, salsolinolwas co-oxidized by dopamine-quinone. When this phenomenon was studied oxygraphically, anunexpected activation of dopamine oxidation was found in the presence of salsolinol. This activationwas related with the enzyme's kinetic mechanism and was named “kinetic synergism”, because abad substrate activated a good one. A possible physiological role is discussed. Keywords: Polyphenol oxidase; banana; salsolinol; latent enzyme; kinetic synergism; dopamine
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