title: Amino acid sequences containing cysteine or half-cystine residues in beta-glucuronidase.
abstract: Amino acid analysis of oxidized or reduced and carboxymethylated beta-glucuronidase have shown the presence of 24 cysteic acid or S-carboxymethylcysteine residues respectively per mole of the tetrameric enzyme. Titration of sulfhydryl groups gave eight cysteine residues, and by difference 16 half-cystine residues per mole. Six peptides containing radiolabelled cysteine residues were isolated from pepsin and chymotrypsin digest of reduced and S-carboxymethylated beta-glucuronidase by ion-exchange chromatography or gel filtration, followed by paper ionophoresis and paper chromatography. The peptides were analysed for amino acids and sequenced by the dansyl-Edman procedure. Peptides containing cysteic acid were selectively recovered from thermolysin digests of performic acid-oxidized glucuronidase. The amino acid sequences confirmed that there were only six different peptide sequences containing either cysteine or half-cystine residues in the tetrameric enzyme, supporting the presence of four identical subunits. These sequences wer: (A)-Val-Asx-Val-Ile-Cys-Val-Asx-Ser-Tyr- (B)-Gly-Asx-Leu-Cys-Ser-Gly- (C)-Phe-Val-Val-Ile-Asx-Glx-Cys-Pro-Gly-Val-Gly- (D)-Val-Val-Cys-Leu- (E)-Gln-Ser-Gly-Cys-Leu-Val-Lys-Gly-Tyr- (F)-Cys-Asp-Arg-Tyr-Gly-Ile-Val-Val-.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003545:Cysteine / Q000032:analysis*; D003553:Cystine / Q000032:analysis*; D005260:Female; D005966:Glucuronidase; D008297:Male; D010413:Penis / Q000201:enzymology*; D010446:Peptide Fragments / Q000032:analysis; D051381:Rats; D012627:Sebaceous Glands / Q000201:enzymology*; D014621:Vagina / Q000201:enzymology*
chemical_list: D010446:Peptide Fragments; D003553:Cystine; D005966:Glucuronidase; D003545:Cysteine