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SURVEYING ALLOSTERIC COOPERATIVITY AND COOPERATIVE INHIBITION IN MUSHROOM TYROSINASE
Author(s) -
HAGHBEEN KAMAHLDIN,
KHALILI MASOUMEH BABAEI,
NEMATPOUR FATMEH SAEID,
GHEIBI NEMATOLAH,
FAZLI MOSTAFA,
ALIJANIANZADEH MEHDI,
JAHROMI SAMANEH ZOLGHADRI,
SARIRI REYHANEH
Publication year - 2010
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.2009.00280.x
Subject(s) - tyrosinase , cooperativity , allosteric regulation , kinetics , chemistry , enzyme kinetics , biochemistry , enzyme , active site , physics , quantum mechanics
In view of the increasing importance of controlling tyrosinase activities, this paper addresses the true kinetics of both activities of MT. Eadie–Hofstee analysis of the kinetics results obtained from the direct spectrophotometric measurements of the cresolase activity in the presence of p ‐coumaric acid and MePAPh and catecholase activity in the presence of caffeic acid and MePACat showed deviation from linearity at lower and higher concentrations of the substrates. Comprehensive kinetics studies on both activities of MT resulted in typical saturation curves of the enzymes displaying mixed cooperativity. The analysis of the double‐reciprocal plots and the slope analysis of the Hill plots of the kinetics data indicate negative cooperativity in both activities. However, it is more pronounced in the cresolase activity. Using the results of some inhibition studies on the cresolase activity, the obtained kinetics results have been explained and discussed in terms of allosteric cooperativity, cooperative inhibition and mixed‐cooperativity.PRACTICAL APPLICATIONS Tyrosinase is a widespread enzyme with great promising capabilities. The past decade research has just started to unfold some other important roles of tyrosinases. In spite of the outstanding progress of the tyrosinase science, there are still some important and immediate issues which have to be addressed. Considering the massive number of different formulations in the healthcare and cosmetic market which contain tyrosinase controlling substances, it seems that elucidation of true nature of the tyrosinase kinetics has become a necessity. Besides, tyrosinases are important subjects of many ongoing researches mainly due to their key role in the enzymatic browning phenomenon which affects the quality of fruits, vegetables and crop products. The outcome of this research can be quite meaningful to the current studies on controlling tyrosinase activities in medicine, nutrition, physiology and biotechnology.