Molecular characterization of a novel β-glucuronidase from Scutellaria baicalensis Georgi

K. Sasaki, F. Taura, Y. Shoyama, S. Morimoto

研究成果: Contribution to journalArticle査読

34 被引用数 (Scopus)


We cloned a gene encoding Scutellaria β-glucuronidase (sGUS) that is involved in the initiation of H2O2 metabolism in skullcap (Scutellaria baicalensis). This gene consists of a 1581-nucleotide open reading frame, the deduced amino acid sequence of which contains an ATP/GTP binding site and a leucine zipper motif. sGUS has apparent similarity to the heparan sulfate-metabolizing β-glucuronidase heparanase but no homology to family 2 β-glucuronidases. In addition, neither the family 2 glycosylhydrolase signature nor family 2 acid-base catalyst was found in this enzyme. These results suggested that sGUS does not belong to the family 2 β-glucuronidases. We modified several residues predicted to act as the acid-base or nucleophilic residue of sGUS by site-directed mutagenesis. Mutations at Glu212 or Glu329 resulted in much lower k(cat)/K(m) values in the mutants as compared with the wild-type enzyme, indicating that these are the acid-base and nucleophilic residues of the active site, respectively. Moreover, similar site-directed mutagenesis confirmed that Tyr281 is also involved in the β-glucuronidase activity. The amino acid sequences of small regions containing these active site residues were conserved in heparanases. As sGUS has various structural characteristics in common with heparanase, we concluded that sGUS and heparanase belong to the same new family.

ジャーナルJournal of Biological Chemistry
出版ステータス出版済み - 9 1 2000

All Science Journal Classification (ASJC) codes

  • 生化学
  • 分子生物学
  • 細胞生物学


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