[Isoform 1]: Lacks catalytic activity due to its inability to undergo the autocatalytic cleavage needed to produce a mature, enzymatically active heterodimer. . [Isoform 2]: Lacks catalytic activity due to its inability to undergo the autocatalytic cleavage needed to produce a mature, enzymatically active heterodimer. . [Isoform 3]: Lacks catalytic activity due to its inability to undergo the autocatalytic cleavage needed to produce a mature, enzymatically active heterodimer. . This is the function of GGT2P (gamma-glutamyltransferase 2, pseudogene, Ensembl gene identifier ENSG00000133475).