The unusual active site of Gal6/bleomycin hydrolase can act as a carboxypeptidase, aminopeptidase, and peptide ligase

Wenjin Zheng, Stephen Albert Johnston, Leemor Joshua-Tor

Research output: Contribution to journalArticle

47 Scopus citations


The Gal6 protease is in a class of cysteine peptidases identified by their ability to inactivate the anti-cancer drug bleomycin. The protein forms a barrel structure with the active sites embedded in a channel as in the proteasome. In Gal6 the C termini lie in the active site clefts. We show that Gal6 acts as a carboxypeptidase on its C terminus to convert itself to an aminopeptidase and peptide ligase. The substrate specificity of the peptidase activity is determined by the position of the C terminus of Gal6 rather than the sequence of the substrate. We propose a model to explain these diverse activities and Gal6's singular ability to inactivate bleomycin.

Original languageEnglish (US)
Pages (from-to)103-109
Number of pages7
Issue number1
StatePublished - Apr 3 1998
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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