Pulse radiolysis studies of electron transfer reaction in molecules of biological interest. I. The reduction of a disulfide bridge by peptide radicals

Journal Article · Mon Dec 01 04:00:00 EST 1975 · Radiat. Res., v. 64, no. 3, pp. 452-466

DOI:https://doi.org/10.2307/3574235· OSTI ID:4081464

Faraggi, M; Redpath, J L; Tal, Y

The reduction of the disulfide bridge in the lipoate anion by peptide radicals and the formate radical ion (CO$sub 2$$sup -$) has been studied using the pulse radiolysis method. Peptide radicals were produced by the reaction of the hydrated electrons with the peptide. It was found that e/sub aq/$sup -$ reacts with diglycine, chloro-acetyl glycine and chloroacetyl diglycine to form a deaminated peptide radical (.CH$sub 2$CONHCH$sub 2$COR). The reaction of e/sub aq/$sup -$ with triglycine at neutral pH forms two radicals: (a) the deaminated radical which is formed when the e/sub aq/$sup -$ reacts with the carbonyl group in an $alpha$ position to the amino group, and (b) an ''electron adduct'' on the carbonyl group of the peptide bond which is formed when the e/sub aq/$sup -$ peptide reaction occurs at other positions. The ''electron adduct'' on the carbonyl radical can be formed by the reaction of the e/sub aq/$sup -$ with acetyl amide. The rate constant for reduction of the lipoate ion disulfide bridge by the deaminated radical was evaluated to be 5 x 10$sup 6$ M$sup - 1$sec$sup -$1, while that for ''electron adduct'' radical and the formate radical is approximately 5 x 10$sup 8$ M$sup -1$ sec$sup -1$. In view of these results a multistep mechanism is suggested for the e/sub aq/$sup -$ reduction of S-S bridge proteins. CO$sub 2$$sup -$ reacts directly with the disulfide bridge. (auth)

• Research Organization: Nuclear Research Center, Beersheba, Israel
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-015025
• OSTI ID: 4081464
• Journal Information: Radiat. Res., v. 64, no. 3, pp. 452-466, Journal Name: Radiat. Res., v. 64, no. 3, pp. 452-466; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

*DISULFIDES-- REDUCTION
*PEPTIDES-- RADIOLYSIS
*RADICALS-- RADIOINDUCTION
*RADIOLYSIS-- BIOCHEMICAL REACTION KINETICS
560111* --Biomedical Sciences
Applied Studies--Radiation Effects--Radiation Effects on Biochemicals--In Vitro
ELECTRONS
GLYCINE
IRRADIATION
N48110* --Life Sciences--Radiation Effects on Biochemicals-- In-Vitro