The 55 kDa tissue transglutaminase cross-linking active isoform TG induces cell death.

Transamidations are calcium-dependent reactions catalyzed by transglutaminase enzymes. Tissue transglutaminase (TG2 or TGC) is a multifunctional protein with a controversial role in apoptosis. The cross-linking function of transglutaminase enzymes has been shown to play a role in cell death.

Induction and translocation of tissue transglutaminase isoforms increased phosphorylation in retinoic acid treated erythroleukemia cells.

Tissue transglutaminase (TGC, TG2, 80 kDa) is inactive in cross-linking reactions and is converted in vitro and in vivo to the TG (55 kDa) active isoform (Fraij in J Cell Biochem 112:2469-2489, 2011). Two isoforms of human TGC were cloned from human erythroleukemia (HEL) cells induced with retinoic acid (RA) and termed TGH, 63 kDa (Fraij et al. in J Biol Chem 267:22616-22673, 1992) and TGH2, 37 kDa.

"Activation of tissue tranglutsaminase by removal of carboxyl-terminal peptides".

Tissue transglutaminase (TGC or TG2) functions as transglutaminase (cross-linking), deamidase, kinase, and disulfide isomerase and its activities are implicated in the pathogenesis of several human diseases. Proteolytic activation of zymogens in the transglutaminase family is not unusual. Plasma transglutaminase (FXIIIa), epidermal transglutaminase (TG 3), transglutaminase-5, and microbial transglutaminase (MTG) can be subjected to proteolysis from specific proteases to generate the active functional enzyme.

Organization and structure of the human tissue transglutaminase gene.

Analysis of the genomic organization of tissue transglutaminase shows that the gene is 32.5 kilobases, contains 13 exons and 12 introns. Our results show that the sites for the two alternative splicing forms of tissue transglutaminase we reported earlier are located within exons 6 and 10 respectively.

A third human tissue transglutaminase homologue as a result of alternative gene transcripts.

A 2.4 kilobase (kb) cDNA encoding a new form of human tissue transglutaminase homologue (TGH2) was isolated from retinoic acid-induced human erythroleukemia cell (HEL) library. Full-length cDNA analysis gives an open reading frame coding for a polypeptide of 349 amino acid residues with a molecular mass of 38,700 Da.