Glutaminyl cyclases (QCs) catalyze the cyclization of N-terminal glutaminyl and glutamyl residues to form pyroglutamic acid (pGlu). Pyroglutamyl peptides and proteins mediate receptor interaction or protein stabilization. For instance, the adipokinetic hormone and corazonin, neuropeptides regulating the glucose concentration in the hemolymph and the heart beat in arthropods, respectively, have been identified as pGlu peptides. (Adapted from
FBrf0202002.)
