N-glycosylated. Proteolytically cleaved at the tripeptide Xaa-Pro-Gln, where Xaa in the P(3) position is mostly lysine. The endoprotease may be of microbial origin. Pyroglutamate formation found on at least Gln-46, Gln-48, Gln-67, Gln-88; Gln-90; Gln-193; Gln-288 Gln-214 and Gln-295, preferentially in diabetic, and head and neck cancer patients. The number of repeats is polymorphic and varies among different alleles. Allele S (short), allele M (medium) and allele L (long) contain 6, 7 and 9 tandem repeats respectively.