Tyrosinase catalyzes the oxidation of mono- and diphenols to o-quinones, which can polymerize and covalently cross-link proteins, but the limited availability and high cost of purified tyrosinase limit broader use. This study recovered tyrosinase from white button mushroom (Agaricus Bisporus) stumps, an underutilized byproduct, and evaluated it for food protein modification. Proteomics identified multiple tyrosinase isozymes (AbPPO3, AbPPO4, AbPPO5), and the crude tyrosinase exhibited optimal activity at pH 7.5 and 45 °C, with a prominent 43 kDa protein band. Ammonium sulfate fractionation (50-70% saturation) increased specific activity; the 50% fraction achieved 4.4-fold purification with 47% activity recovery. Effects of chemical modulators, metal ions, salts, reductants, chelators, and inhibitors were systematically assessed. Endogenous proteolysis hindered cross-linking, but partial purification and EDTA/PMSF suppressed protease activity, enabling tyrosinase-catalyzed casein polymerization. These results demonstrate a cost-effective source to valorize mushroom waste into a tyrosinase biocatalyst for protein cross-linking.
Tran et al. (2026) studied this question.