Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:3.4.21.4 (
trypsin
)
42,187
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Alkylation of reduced Escherichia coli thioredoxin by the episulfonium ion derived from S-(2-chloroethyl)glutathione (
CEG
) at physiologic pH resulted in at least three different alkylation products. These adducts were separated by reverse phase chromatography, digested with
trypsin
, and peptide-mapped. The peptide containing the active site cysteines was collected and sequenced by tandem mass spectrometry. Results indicate that the site of alkylation was at Cys-32 exclusively with no alkylation at Cys-35. Raising the pH above the pKa of Cys-35 to ionize the thiol before reacting with the episulfonium ion of
CEG
did not lead to alkylation at Cys-35, suggesting that a steric factor prevents the alkylating moiety of
CEG
from accessing this cysteine. A tryptic digest of a minor bis-adduct yielded an alkylated peptide which contained tyrosine, an amino acid known to be alkylated at its hydroxyl group by
CEG
. Sequencing by tandem mass spectrometry, however, was unsuccessful due to fragmentation of the alkylating moiety from the peptide. Results of this study confirm that the episulfonium ion of
CEG
can adduct thioredoxin at the active site and may have important toxicologic significance regarding the mechanism of 1,2-dichloroethane toxicity.
...
PMID:Alkylation of Escherichia coli thioredoxin by S-(2-chloroethyl)glutathione and identification of the adduct on the active site cysteine-32 by mass spectrometry. 855 8
