Paper Information

Journal:   BIOLOGICAL SCIENCES (DANISH-I ZISTI-I IRAN)   SUMMER 2008 , Volume 3 , Number 2; Page(s) 27 To 35.
 
Paper: 

INHIBITORY EFFECT OF SOME NEW SYNTHESIZED ALKYL XANTHATE ON THE CRESOLASE ACTIVITY OF MUSHROOM TYROSINASE

 
 
Author(s):  ALIJANIANZADEH M.*
 
* DEPARTMENT OF BIOLOGY, SCIENCE FACULTY, VARAMIN BRANCH, ISLAMIC AZAD UNIVERSITY, VARAMIN, IRAN
 
Abstract: 

Three iso-alkyldithiocarbonates (xanthates), as sodium salts, C3H7OCS2Na (I), C4H9OCS2Na (II) and C5H11OCS2Na (III) were synthesized, by the reaction between CS2 and the corresponding iso-alcohol in the presence of NaOH. These compounds were examined for inhibition of cresolase activity of mushroom tyrosinase (MT) from a commercial source of Agricus bisporus.4- [(4-methylphenyl) azo] -phenol (MePAPh) were used as synthetic substrate for the enzyme for the cresolase reaction. Lineweaver-Burk plots showed different patterns of mixed and competitive inhibition for the three xanthates. For cresolase activity, I and II showed a mixed inhibition pattern but III showed a competitive inhibition pattern. These new synthesized compounds are potent inhibitors of MT with Ki values of 9.8, 7.2 and 6.1 microM for cresolase inhibitory activity, for compound-I, -compound-II and compound-III, respectively. Both substrate and inhibitor can be bound to the enzyme with negative cooperativity between the binding sites (a>1) and this negative cooperativity increases with increasing length of the aliphatic tail in these compounds in cresolase activity. The cresolase inhibition is related to the chelating of the copper ions at the active site by a negative head group (S-) of the anion xanthate, which leads to similar values of Ki for all three xanthates.

 
Keyword(s): MUSHROOM TYROSINASE, ALKYL XANTHATE, MIX INHIBITION, COMPETITIVE INHIBITION, INHIBITION CONSTANT
 
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