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First derivative synchronous fluorometric method to continuously measure monophenolase activity.

Ling Zhang1, Jiaze Li1, Xiawen Wang1

  • 1Department of Pharmaceutical and Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, 610065, China.

Enzyme and Microbial Technology
|September 7, 2021
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Summary

A new fluorometric assay accurately measures tyrosinase monophenolase activity, enabling kinetic analysis and inhibitor discovery for cosmetics and medicine.

Keywords:
BorateFirst derivative synchronous fluorescenceInhibitorMonophenolaseTyrosine

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Area of Science:

  • Biochemistry
  • Enzymology

Background:

  • Tyrosinase is crucial for melanin production, possessing both monophenolase and diphenolase activities.
  • Accurate quantification of tyrosinase activity is essential for understanding melanin biosynthesis and developing related products.

Purpose of the Study:

  • To develop a rapid and selective first derivative synchronous fluorometric assay for directly monitoring tyrosinase monophenolase activity.
  • To analyze the enzyme kinetics and inhibition of tyrosinase monophenolase activity.

Main Methods:

  • A first derivative synchronous fluorometric assay was established using a zero-crossing point at 322 nm (Δλ = 67 nm) for selective tyrosine quantification.
  • Tyrosine consumption and monophenolase activity were monitored over time to determine kinetic parameters.
  • The effect of zinc ions on monophenolase activity was investigated to determine inhibition characteristics.

Main Results:

  • The assay achieved a limit of detection (LOD) of 0.54 μM for tyrosine and 0.0706 U⋅mL⁻¹ for monophenolase activity.
  • Kinetic parameters (Michaelis-Menten constant and maximum speed) were determined as 21.83 μM and 1.12 μM⋅min⁻¹, respectively.
  • Zinc ions were found to competitively inhibit monophenolase activity with an IC₅₀ of 14.36 μM.

Conclusions:

  • The developed assay provides a simple, rapid, and selective method for analyzing tyrosinase monophenolase activity and kinetics.
  • This method has significant potential for screening tyrosinase inhibitors for pharmaceutical and cosmetic applications, as well as for industrial synthesis.