Catalyzes the cross-linking of proteins and the conjugation of polyamines to proteins. Responsible for cross-linking epidermal proteins during formation of the stratum corneum. Involved in cell proliferation (PubMed:26220141). L-glutaminyl-[protein] + L-lysyl-[protein] = [protein]-L-lysyl-N(6)-5-L-glutamyl-[protein] + NH4(+) Binds 1 Ca(2+) ion per subunit. Interacts with PLAAT4. Palmitoylated. The membrane anchorage region possesses a cluster of five cysteines within which fatty acid(s) may become thioester-linked. It is subject to phorbol ester-stimulated phosphorylation and is hypersensitive to proteolysis, which releases the enzyme in a soluble form. Tyrosine-phosphorylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the transglutaminase superfamily. Transglutaminase family.