It has been shown [1,2,3] that several enzymes from various prokaryotic and eukaryotic organisms which are involved in the hydrolysis of amides (amidases) are evolutionary related. These enzymes are listed below.

• Indoleacetamide hydrolase (EC 3.5.1.-), a bacterial plasmid-encoded enzyme that catalyzes the hydrolysis of indole-3-acetamide (IAM) into indole-3- acetate (IAA), the second step in the biosynthesis of auxins from tryptophan.
• Acetamidase from Emericella nidulans (gene amdS), an enzyme which allows acetamide to be used as a sole carbon or nitrogen source.
• Amidase (EC 3.5.1.4) from Rhodococcus sp. N-774 and Brevibacterium sp. R312 (gene amdA). This enzyme hydrolyzes propionamides efficiently, and also at a lower efficiency, acetamide, acrylamide and indoleacetamide.
• Amidase (EC 3.5.1.4) from Pseudomonas chlororaphis.
• 6-aminohexanoate-cyclic-dimer hydrolase (EC 3.5.2.12) (nylon oligomers degrading enzyme E1) (gene nylA), a bacterial plasmid encoded enzyme which catalyzes the first step in the degradation of 6-aminohexanoic acid cyclic dimer, a by-product of nylon manufacture [4].
• Glutamyl-tRNA(Gln) amidotransferase subunit A [5].
• Mammalian fatty acid amide hydrolase (gene FAAH) [6].
• A putative amidase from yeast (gene AMD2).
• Mycobacterium tuberculosis putative amidases amiA2, amiB2, amiC and amiD.

All these enzymes contains in their central section a highly conserved region rich in glycine, serine, and alanine residues. We have used this region as a signature pattern.