Glutaminyl Peptide Cyclotransferase Like Protein (QPCTL)

QPCTL, also termed Iso-glutaminyl cyclase catalyzes the intramolecular cyclization of N-terminal glutamine residues into pyroglutamic acid with liberation of ammonia and the intramolecular cyclization of N-terminal glutamate residues into pyroglutamic acid with liberation of water.

Glutaminyl cyclase (QPCT) catalyzes the intramolecular cyclization of N-terminal glutamine residues into pyroglutamic acid liberating ammonia. In contrast, the physiological function of the plant QC is less clear. In case of the enzyme from C. papaya, a role in the plant defence against pathogenic microorganisms was suggested. Putative QCs from other plants were identified by sequence comparisons. The physiological function of these enzymes, however, is still ambiguous.