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A human de‐ubiquitinating enzyme with both isopeptidase and peptidase activities in vitro
Author(s) -
Falquet Laurent,
Paquet Nicole,
Frutiger Séverine,
Hughes Graham J.,
Hoang-Van Khan,
Jaton J.-C.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)01451-6
Subject(s) - enzyme , ubiquitin , in vitro , cleavage (geology) , biochemistry , peptide , monomer , proteolysis , biology , ubiquitin ligase , chemistry , stereochemistry , microbiology and biotechnology , polymer , gene , paleontology , organic chemistry , fracture (geology)
Some enzymatic and physicochemical properties of a human ubiquitin‐specific isopeptidase are reported. The enzyme was purified to homogeneity from red blood cells and its specificity towards polymeric ubiquitin substrates suggests a de‐ubiquitinating activity capable of cleaving ‘head‐to‐tail’ polyUb chains as well as isoamide ‘branched’ Ub dimers. K M values show a 10 fold preference for the cleavage of branched Ub dimers over head‐to‐tail Ub dimers. The enzymatic activity can be strongly inhibited by various peptides containing either of the cleavage site sequences found in Ub polymers, but not by unrelated peptides. The enzyme is monomeric under reducing conditions and exhibits a globular shape with an average diameter of 9 nm, an S 20,w value of 5.2 S and a molar mass of 110 kDa ± 10%. Because the enzyme cleaves both peptide‐linked and isopeptide‐linked Ub moieties from substrates, we propose to name it de‐ubiquitinase rather than isopeptidase.