Cystine residues beta elimination

Elimination reactions 526, 530, 677—690 beta, of cystine residues 85 conjugative 689 decarboxylative 689 facilitation by carbonyl group 681 of y substituent 746 of PLP-dependent enzymes 742 reversibility 690 Ellman s reagent 125,125s Elongation factor EF-Tu 558 Elongin complex 564... 

To ascertain the upper limit of protein thermostability and to evaluate the effect of additional disulfide bridges on the enhancement of protein thermostability, additional cysteine residues were introduced into several unrelated proteins by site-directed mutagenesis and deactivation behavior tested at 100°C (Volkin, 1987). All the proteins investigated underwent heat-induced beta-elimination of cystine residues in the pH 4—8 range with first-order kinetics and similar deactivation constants kj that just depended on pH 0.8 0.3 h-1 at pH 8.0 and 0.06 0.02 h 1 at pH 6.0. These results indicate that beta-elimination is independent of both primary amino acid sequence and the presence of secondary structure elements. Elimination of disulfides produces free thiols that cause yet another deleterious reaction in proteins, heat-induced disulfide interchange, which can be much faster than beta-elimination. 

The mechanism of disulfide reduction by phosphines is hypothesized to involve a stable intermediate containing a sulphur-phosphorous bond (6). Beta elimination would yield the phosphine sulfide and dehydroalanine. The formation of relatively stable adducts between cystine-containing peptides and the reagent was confirmed by mass spectrometry for several peptides with the major adduct representing one reagent molecule per cystine residue. 

Beta elimination high-temperature treatment of proteins leads to destmction of disulfide bonds as a result of yS-elimination from the cystine residue. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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