Photo-Oxidation of the Serine,Threonine,and Cystine Side-Chains of Wool to Carbonyl Derivatives

Abstract

Irradiation of wool by simulated sunlight, followed by reduction with sodium borotritide and acid hydrolysis, gives radiolabeled serine, threonine, and allo-threonine. Application of the same procedure to wool in which cystine residues have been reduced and carboxymethylated, or in which serine and threonine residues have been sulphated, gives the same three labeled amino acids, but in different pro portions. Our interpretation of these results is (1) that serine and cystine residues are photo-oxidized to α-formylglycine residues, which borotritide reduction converts to ²H-serine residues, and (2) that threonine residues are photo-oxidized to α-acetylglycine residues, which reduction converts to threonine and allo-threonine residues. Circumstantial evidence for the photo-oxidation of serine (and possibly cystine) residues to α-carboxyglycine residues is also presented.

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