[1] They are believed to be represented in all major enzyme families in the kingdoms of life, where they have important signaling and metabolic functions, many of which are only now coming to light.
They are also suggesting new ways to target and interpret cellular signalling mechanisms using small molecules and drugs.
[5] The most intensively analyzed, and certainly the best understood pseudoenzymes in terms of cellular signalling functions are probably the pseudokinases, the pseudoproteases and the pseudophosphatases.
[6][7] The difference between enzymatically active and inactive homologues has been noted (and in some cases, understood when comparing catalytically active and inactive proteins residing in recognisable families) for some time at the sequence level,[8] owing to the absence of key catalytic residues.
[20][21] The role of pseudoenzymes as "pseudo scaffolds" has also been recognised [22] and pseudoenzymes are now beginning to be more thoroughly studied in terms of their biology and function, in large part because they are also interesting potential targets (or anti-targets) for drug design in the context of intracellular cellular signalling complexes.