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Mushroom tyrosinase has an ascorbate oxidase activity
J R Ros1, J N Rodríguez-López, R Varón-Castellanos
1Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Murcia, Spain.
Biochemistry and Molecular Biology International
|June 1, 1995
Summary
Mushroom tyrosinase exhibits ascorbate oxidase activity, reacting with L-ascorbic acid. This enzymatic activity is linear with enzyme concentration and optimal at pH 7.5, with a Michaelis constant of 2.69 mM.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Mushroom tyrosinase is a well-known enzyme involved in melanin biosynthesis.
- Its potential role in oxidizing other substrates like L-ascorbic acid requires further investigation.
Purpose of the Study:
- To investigate the interaction between mushroom tyrosinase and L-ascorbic acid.
- To determine if mushroom tyrosinase possesses ascorbate oxidase activity.
- To characterize the kinetic parameters and optimal conditions for this activity.
Main Methods:
- Oxymetric assays were employed to monitor the reaction.
- Enzyme kinetics were analyzed to determine the Michaelis constant (Km) and reaction linearity.
- pH optima were assessed.
Main Results:
- Evidence was obtained for ascorbate oxidase activity of mushroom tyrosinase.
- The enzymatic activity demonstrated a clear linear relationship with enzyme concentration.
- The Michaelis constant for L-ascorbic acid was determined to be 2.69 +/- 0.11 mM.
- Optimal enzyme activity was observed at pH 7.5.
Conclusions:
- Mushroom tyrosinase exhibits significant ascorbate oxidase activity.
- The study provides kinetic parameters and optimal conditions for this enzymatic reaction.
- A potential reaction mechanism involving different enzymatic forms of tyrosinase is proposed.