TGM2 and leukemia: In particular, in leukemia cells, two variants of the TGM2 transcript have been described: variant 2, which encodes the 63 kDa TGH protein and lacks the GTP binding site and therefore always active [17]; variant 3-HEL, which encodes the 37 kDa TGH2 protein and lacks cysteine in the catalytic core, so it is inactive and cannot be activated [18].