[Objective] We aimed to reveal a novel function of bagZH in Streptomyces sp. Tü4128, which encoded a tyrosinase-like copper enzyme.[Methods] The bagZH gene was deleted through homologous recombination, and the secondary metabolites were detected and analyzed by HPLC and LC-ESI-MS. The activity of the BagH enzyme expressed by E. coli BL21(DE3) was measured by biochemical assays. The catalytic products of the enzyme were analyzed by LC-ESI-MS, in which o-aminophenol and 3,4-AHBA were used as substrates.[Results] HPLC analysis showed that the production of bagremycin significantly decreased when bagZH was deleted. Complementation of bagZH gene expression cassettes in the mutant increased the accumulation of bagremycin. LC-ESI-MS results showed that the molecular weight of the new product with a retention time of 3.18 min was 286.32 g/mol, which was consistent with the predicted molecular weight of the product synthesized by esterification of 3,4-AHBA in vivo. In vitro biochemical analysis demonstrated that BagH can catalyze the oxidation of o-aminophenol (protecting group).[Conclusion] Our findings revealed for the first time that bagZH participated in the biosynthesis of bagremycin by encoding a tyrosinase-like copper enzyme. BagH protected the biosynthetic intermediates by catalyzing the oxidation of 3,4-AHBA to a nitroso derivative (protecting group). After condensation with p-coumanic acid, the nitroso-group is reduced by a reductase in vivo to generate bagremycin A and B. The results obtained in this study provide a basis and reference for in-depth study of the mechanism of bagremycin and rational design and transformation of high-yielding strains.