BMC Biol. 2016 Nov 11;14(1):98.
"A pseudoenzyme contains a protein domain with a fold that resembles, or is predicted to resemble, a catalytically active, conventional protein domain counterpart. However, the pseudoenzyme possesses vestigial or zero catalytic activity owing to the absence of key catalytic amino acids or motifs. Such proteins have been long acknowledged to exist within proteomes and have also been termed nonenyzmes . In a sense, pseudoenzymes can be considered to be ‘zombie’ versions of proteins: ‘undead’ in the sense that they still perform important cellular functions, but at the same time ‘dead’ since they possess negligible enzymatic activity relative to their catalytically active cousins."