Enzymes are biological catalysts that are very effective in removing organic pollutants from water [1]. Horseradish peroxidase is an enzyme commonly used in wastewater treatment due to its ability to oxidize a wide range of organic pollutants. Most commonly, enzymes are applied immobilized on some solid supports, such as magnetic nanoparticles. The immobilization of peroxidases on magnetite nanoparticles not only increases their stability and catalytic efficiency but also facilitates the efficientseparation and reuse of the enzyme. [2]. Magnetic nanoparticles are a promising solid support due to their unique properties, such as large surface area, magnetic response, and easy recovery [3]. The performance of magnetite particles as enzyme carriers could be significantly improved if their synthesis is carried out in the presence of plant extracts [4]. Bioactive components, such as polyphenols, can be incorporated into the structure of the magnetite particles, increasing the presence of functional groups suitable for binding the enzyme to the magnetite surface.In this work, the properties of immobilized horseradish peroxidase on biofunctionalized magnetite particles were investigated. The magnetite particles were synthesized from iron II and III sulfate salts in the presence of tangerine peel extracts. The plant extraction was carried out by maceration at room temperature (25°C) using natural deep eutectic solvent (fructose and glycerol in a ratio of 1:4) for 10 min. The extract obtained had a medium content of total phenols (0.009 mg CAE/mg) and total flavonoids(0.002 mgER/mg), and showed high anti-radical DPPH ability (IC50 value was 0.96 mg/g). The Reducing Power test showed moderate activity, with an EC50 value of 2.255 mg/g. The synthesized biofunctionalized magnetite particles were used as a solid support for the immobilization of peroxidase through glutaraldehyde. The obtained immobilized enzyme showed relatively high enzymatic activity (8.5 U/g), with the highest activity measured at pH 6 and 50°C. The immobilized enzyme retains more than75% of its activity at temperatures of 25-50°C and pH values of 6-8, and could be used in a larger number of consecutive cycles. It can be concluded that immobilized peroxidase on biofunctionalized magnetite particles has potential for application as a biocatalyst in water treatment.