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Abstract
The polyphenol oxidase (LsPPO) from a wild edible mushroom Lactarius salmonicolor was purified using a Sepharose 4B-L-tyrosine-p-amino benzoic acid affinity column. At the optimum pH and temperature, the KM and VMax values of LsPPO towards catechol, 4-methylcatechol and pyrogallol were determined as 0.025 M & 0.748 EU/mL, 1.809 × 10− 3 M & 0.723 EU/mL and 9.465 × 10− 3 M & 0.722 EU/mL, respectively.
Optimum pH and temperature values of LsPPO for the three substrates above ranged between the pH 4.5–11.0 and 5–50°C. Enzyme activity decreased due to heat denaturation with increasing temperature. Effects of a variety of classical PPO inhibitors were investigated opon the activity of LsPPO using catechol as the substrate. IC50 values for glutathione, p-aminobenzenesulfonamide, L-cysteine, L-tyrosine, oxalic acid, β-mercaptoethanol and syringic acid were determined as 9.1 × 10− 4, 2.3 × 10− 4 M, 1.5 × 10− 4 M, 3.8 × 10− 7 M, 1.2 × 10− 4 M, 4.9 × 10− 4 M, and 4 × 10− 4 M respectively. Thus L-tyrosine was by far the most effective inhibitor. Interestingly, sulfosalicylic acid behaved as an activator of LsPPO in this study.
Acknowledgements
The authors would like to thank the group researchers Murat Sayın, Aysegul Sahin and Semra Isık for their technical laboratory support, and also Balikesir University, Research Center of Applied Sciences (BURCAS / Balikesir, Turkey) for providing the research facilities. We also thank Dr. Malcolm Lyon (University of Manchester. Paterson Institute for Cancer Research) for his invaluable contribution to this paper.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.