Hydrolases;
Acting on peptide bonds (peptidases);
Cysteine endopeptidases
Reaction(IUBMB)
Hydrolyses glutaminyl bonds, and activity is further restricted by preferences for the amino acids in P6 - P1' that vary with the species of potyvirus, e.g. Glu-Xaa-Xaa-Tyr-Xaa-Gln!(Ser or Gly) for the enzyme from tobacco etch virus. The natural substrate is the viral polyprotein, but other proteins and oligopeptides containing the appropriate consensus sequence are also cleaved.
Comment
The potyviruses cause diseases in plants, and inclusion bodies appear in the host cell nuclei; protein a of the inclusion bodies is the endopeptidase. The enzyme finds practical use when encoded in vectors for the artificial expression of recombinant fusion proteins, since it can confer on them the capacity for autolytic cleavage. It is also reported that transgenic plants expressing the enzyme are resistant to viral infection. Type example of peptidase family C4.
