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 and in the dorsal part of the prostate. Not expressed in the brain, heart, kidney, liver, lung, muscle, pancreas, spleen, stomach, testis and thymus. Belongs to the transglutaminase superfamily. Transglutaminase family.