Linked Life Data

17764150

Source:http://linkedlifedata.com/resource/pubmed/id/17764150

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
9
pubmed:dateCreated
2007-9-18
pubmed:abstractText
The kinetics and mechanisms of the hydrolysis of cysteine thiosulfinate ester (CyS(O)SCy ( x- ), x = 0-2) have been investigated by stopped-flow spectrophotometry between pH 6 and pH 14. The rate-limiting reaction of hydroxide is observed for pH < 13. More complicated kinetics are observed above pH 13, where the hydrolysis of CyS(O)SCy (2-) can be fast relative to subsequent reactions. The eventual products of hydrolysis are a 1:1 molar ratio of cystine (CySSCy) and cysteine sulfinic acid (CySO 2H) under all reaction conditions. The rate of hydrolysis is dependent upon the proton state of CyS(O)SCy ( x- ). Furthermore, cysteine thiosulfonate ester (CyS(O) 2SCy) was observed as an intermediate during the hydrolysis of CyS(O)SCy ( x- ) at lower pH. CyS(O) 2SCy eventually hydrolyzes to give stoichiometric amounts of CySSCy and CySO 2H. However, CySO 2H is observed under some conditions for which hydrolysis of CyS(O) 2SCy is relatively slow, thus suggesting multiple hydrolysis pathways for CyS(O)SCy ( x- ). The mechanism up to the rate-limiting step is proposed to be as follows: CyS(O)SCy (0) = H (+) + CyS(O)SCy (-), p K a3 = 7.32; CyS(O)SCy (-) = H (+) + CyS(O)SCy (2-), p K a4 = 7.92; CyS(O)SCy (0) + OH (-) --> products, P 0 k 0 = (5.0 +/- 0.01) x 10 (3) M (-1) s (-1); CyS(O)SCy (-) + OH (-) --> products, P 1 k 1 = 60 +/- 18 M (-1) s (-1); and CyS(O)SCy (2-) + OH (-) --> products, P 2 k 2 = 0.36 +/- 0.01 M (-1) s (-1), where P x is a constant (1 </= P x </= 3) that accounts for the partitioning between the possible hydrolysis pathways and the stoichiometries of their net reactions.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0893-228X
pubmed:author
pubmed:issnType
Print
pubmed:volume
20
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1364-72
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
Reactive sulfur species: kinetics and mechanism of the hydrolysis of cysteine thiosulfinate ester.
pubmed:affiliation
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural