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Title: Density functional theory calculations on biological S-transfer: Insight into the mechanism of rhodanese
Authors: Dey, Subal
Dey, Abhishek
Keywords: Density functional calculations
S-transfer reactions
Cyanide detoxification
Issue Date: Sep-2011
Publisher: NISCAIR-CSIR, India
Abstract: Biological sulfur transfer (S-transfer) is a key step in the synthesis of metabolites, CN- detoxification and assembly of iron-sulfur clusters. Computational results addressing the thermodynamics of the S-transfer reactions from thiosulfate (natural S-donor) to HCN and thiol are presented. These calculations indicate that S-transfer from thiosulfate to HCN and thiol is possible only in the anionic forms of these species. However these species have pKa values significantly higher than physiological pH value (i.e., they are protonated in physiological pH and incapable of S-transfer). In the rhodanese active site, basic residues are present to deprotonate the catalytic cysteine group which accepts the S-atom from thiosulfate. The resultant perthiol species transfer S-atom to CN- in a synchronous S-atom and H+ transfer step facilitated by the two arginine residues present in the rhodanese active site.  Based on these calculations, a mechanism is proposed for the rhodanese catalyzed CN- detoxification pathway.
Page(s): 1457-1462
CC License:  CC Attribution-Noncommercial-No Derivative Works 2.5 India
ISSN: 0975-0975(Online); 0376-4710(Print)
Source:IJC-A Vol.50A(09-10) [September-October 2011]

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