title: Chemical characterization of an alkali-labile bond in the polypeptide of proline reductase from Clostridium sticklandii.
abstract: In previous studies, it was shown that a 4600-dalton pyruvate-containing peptide is released from proline reductase by mild alkali treatment. The alkali-sensitive bond proved to be between Ser-Glu, and it was suggested that an ester, rather than a peptide linkage, might be involved. In the present study, the effects of additional esterolytic reagents, (I) LiBH4 and (II) NH2OH, on proline reductase have been investigated and compared with 0.1 N NaOH-induced cleavage. Treatment with reagents I and II released a peptide identical with the peptide released by alkali as judged by electrophoretic mobility on thin layer sheets, COOH-terminal analyses, and amino acid compositional studies. The glutamic acid residue is converted to alpha-amino-delta-hydroxyvaleric acid after reductive cleavage with LiBH4. The liberation of the peptide fragment by the relatively specific esterolytic reagent, LiBH4, provides additional support of the presence of an ester linkage in native proline reductase.
mesh_terms: D000594:Amino Acid Oxidoreductases; D000596:Amino Acids / Q000032:analysis; D001894:Borohydrides; D003013:Clostridium / Q000201:enzymology*; D005971:Glutamates / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D010446:Peptide Fragments / Q000032:analysis
chemical_list: D000596:Amino Acids; D001894:Borohydrides; D005971:Glutamates; D010446:Peptide Fragments; C022452:D-proline reductase (dithiol); D000594:Amino Acid Oxidoreductases