CHARACTERIZATION OF PARTIALLY PURIFIED TYROSINASE ISOLATED FROM BITTER KOLA (GARCINIA KOLA)
Authors: Itakorode B.O. , Agboola O.E. , Adeboye M.B. , Benedict C.C. , Terkula K.N. , Aregbesola M.F. , Ajayi M.O. 
Published: January 2022

Objective: Tyrosinase is a glycosylated, copper-containing oxidase that catalyzes the first two steps of mammalian melanogenesis as well as enzymatic browning events in damaged fruits during post-harvest handling and processing. Human skin hyperpigmentation and enzymatic browning in fruits are both undesirable. In this study, the properties and inhibitory effect of some compounds on bitter kola tyrosinase were investigated.
Methods: Bitter kola tyrosinase was isolated and characterized using standard protocols. Partial purification was carried out on Sephadex G-100 loaded column chromatography.
Results: Bitter kola tyrosinase was purified with a specific activity of 3.5 U/mg protein, purification fold of 2.4 and a yield of 34%. The optimum pH value was found to be 6.0 while the optimum temperature value for maximum enzyme activity was observed at 60°C. The enzyme was stable at 40oC for 20 minutes. Metals such as NaCl, KCl, MgCl2 and CaCl2 had inhibitory effect on the activity; though MgCl2 and CaCl2 had minimal effect. Also, EDTA, β-marcaptoethanol and glutathione greatly inhibited the enzyme activity at all the tested concentration.
Conclusion: The properties of bitter kola tyrosinase compare very well with the tyrosinase from other sources. Also, the study was able to establish the inhibitory effect of some compounds and this could be applied in food processing industries.

Peer Review History:
Received: 2 November 2021; Revised: 11 December; Accepted: 25 December, Available online: 15 January 2022
Academic Editor: Dr. A.A. Mgbahurike, University of Port Harcourt, Nigeria, amaka_mgbahurike@yahoo.com
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Received file: Reviewer's Comments:
Average Peer review marks at initial stage: 6.0/10
Average Peer review marks at publication stage: 7.5/10
Reviewers:
Dr. Nazim Hussain, North East Frontier Technical University, Arunachal pradesh, India, nhussain116@gmail.com
Ahmad Najib, Universitas Muslim Indonesia, Makassar, Indonesia, ahmad.najib@umi.ac.id
Prof. Dr. Ali Gamal Ahmed Al-kaf, Sana'a university, Yemen, alialkaf21@gmail.com
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