Associated with the mammalian reproductive process. Plays an important role in the formation of the seminal coagulum through the cross-linking of specific proteins present in the seminal plasma. Transglutaminase is also required to stabilize the copulatory plug. L-glutaminyl-[protein] + L-lysyl-[protein] = [protein]-L-lysyl-N(6)-5-L-glutamyl-[protein] + NH4(+) Binds 1 Ca(2+) ion per subunit. Homodimer. Expressed in the coagulating gland, the dorsal part of the prostate and in semen (at protein level). Expressed at low levels in the lateral prostate and seminal vesicle. Not expressed in the epididymis, kidney, liver, serum, sperm plug, testes and ventral prostate. Androgen dependent, as shown by the decrease in the level of the protein following castration. The N-terminus is blocked. Probably linked to the cell membrane via a lipid-anchor, possibly a GPI-anchor. N-glycosylated on 2 Asn residues by a high mannose oligosaccharide consisting of five mannose residues and a fucosylated biantennary complex glycan. Belongs to the transglutaminase superfamily. Transglutaminase family.