title: Stability, structural and suicide inactivation changes of mushroom tyrosinase after acetylation by N-acetylimidazole.
abstract: Modification (acetylation) of Tyr residues with N-acetylimidazole protects outstandingly mushroom tyrosinase (MT) from the suicide inactivation in the presence of its catecholic substrate, 4-[(4-methylbenzo) azo]-1,2-benzenediol. UV spectrophotometric experiments and differential scanning calorimetry (DSC) studies indicated a decrease in kinetic stability of the enzyme alongside with increase in its thermal stability as well as its stability against n-dodecyl trimethylammonium bromide as a denaturizing agent. Pace analysis resulted in standard Gibbs free energy values of 46.54 and 52.09 kJ/mol in the absence of denaturant for native and modified enzyme, respectively. Structural studies by circular dichroism (CD) spectrophotometry showed that modification did not have major impact on the secondary structure of MT; however, induced some changes in its tertiary structure. The near-UV CD results revealed that the modification had enhanced intramolecular van der Waals interactions in the enzyme structure, which was in coincidence with its thermodynamic stability.
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran. saboury@chamran.ut.ac.ir
authors.forename: A A
authors.initials: AA
authors.lastname: Saboury
authors.forename: F
authors.initials: F
authors.lastname: Karbassi
authors.forename: K
authors.initials: K
authors.lastname: Haghbeen
authors.forename: B
authors.initials: B
authors.lastname: Ranjbar
authors.forename: A A
authors.initials: AA
authors.lastname: Moosavi-Movahedi
authors.forename: B
authors.initials: B
authors.lastname: Farzami
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D002151:Calorimetry; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D004798:Enzymes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013053:Spectrophotometry; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D004798:Enzymes; D007093:Imidazoles; D000644:Quaternary Ammonium Compounds; D014442:Monophenol Monooxygenase; C022806:dodecyltrimethylammonium; C012160:N-acetylimidazole