Abstract

Tyrosinase catalyzes formation of browning in plants, foods and vegetables. Sweet potato (Ipomea batatas) undergoes browning after harvesting or during post-harvest operations leading to spoilage and loss of economic value. The physico-chemical properties of purified tyrosinase from I. batatas are here described with a view to providing information on the suitability or otherwise of the enzyme for several industrial and biotechnological processes. The enzyme was purified using new approach resulting into final yield and purification fold of 76% and 7.1, respectively. The molecular weight (native) was 48.3 ± 2.5 kDa as estimated on Sephadex G-100. Highest tyrosinase activity was obtained at pH 6.5 while that of temperature was 50°C. Kinetic parameters studies resulted to 2.5 ± 1.2 mM and 451 ± 23.7 units/mg for Michaelis constant (K_m) and maximum velocity (V_max), respectively. This led to catalytic efficiency, k_cat/K_m of 1.45 × 10⁵ s^-1 M^-1. It was concluded that, tyrosinase from I. batatas possesses remarkable properties that could be exploited for biotechnological processes.

Key words: Polyphenols, Solanaceae, biotechnology, biocatalysis.