Some physicochemical properties of tyrosinase from sweet potato (Ipomea batatas)

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 × 10 5 s -1 M -1 . It was concluded that, tyrosinase from I. batatas possesses remarkable properties that could be exploited for biotechnological processes.

Biochemical properties of purified polyphenol oxidase from bitter leaf (Vernonia amygdalina)

“…Plants PPOs have different enzymatic activity on various phenolic substrates. The position and number of hydroxyl groups have remarkable effect on the PPO’s activity [ 20 ]. In addition, the specificity of polyphenol oxidase towards substrates are also influenced by the plant cultivar [ 26 ].…”

“…Most of the PPO in plants are found in the chloroplasts of photosynthetic cells and the leucoplasts of storage cells [ 16 ]. PPO has been extracted, purified and characterized in various plants including avocado [ 17 ], banana pulp [ 18 ], apple fruit [ 19 ] and sweet potato [ 20 ].…”

Biochemical Properties of Purified Peroxidase from Rhizome of Turmeric (Curcuma longa L.)

“…The plant peroxidases belong to Class III peroxidase, they participate in diverse physiological and biochemical activities having diverse function in the plant which include cell wall edi cation, cellular growth, differentiation and development, in hormone catabolism, lignin polymerization, suberization, fruit growth and ripening, ethylene biosynthesis, plasma membrane redox systems and the generation of H 2 O 2 , auxin metabolism, senescence, and defense mechanisms against abiotic and biotic stress (2016; Kidwai et al, 2020 ). Despite numerous roles in plant metabolism, most plant oxidoreductases such as tyrosinase, polyphenol oxidases and peroxidase cause undesirable browning in plant tissues (Ilesanmi and Adewale, 2020;Ávila-Alvarez et al, 2022 andIlesanmi et al, 2022). However, in isolated and puri ed form, they constitute the majority of the class of highly applicable enzymes in biotechnology (Ali et al, 2019).…”

Kinetics and molecular docking of purified polyphenol oxidase from rhizome of turmeric (Curcuma longa L.)

“…They are a group of copper-containing enzymes that catalyze the o-hydroxylation of monophenols to o-diphenols as well as the oxidation of odiphenols to quinones in the presence of oxygen [2]. Polyphenol oxidase is broadly distributed among animals, fungi, and plants, although the studies are more extensive in plants [3,4]. The study of PPOs in plants has focused primarily on their role in the process of postharvest browning, whereby cut or damaged plant tissues turn brown due to the polymerization of PPO-generated quinones, generating phyto-melanins [5].…”