Disintegrin and metalloproteinase domain-containing protein 20 is an enzyme that in humans is encoded by the ADAM20gene. It is a membrane disintegrin-metalloprotease that belongs to the ADAM family. It is exclusively expressed in Testes and is similar to sperm cell-specific fertilins -alpha and -beta.
Its cDNA is tightly linked to marker SHGC-36001 on chromosome 14q24.1. ADAM20 is related to fertilin α (ADAM1A/B pseudogene), fertilin β (ADAM2), and fertilin γ (ADAM9). In humans, fertilin α has recently been deactivated so ADAM20 may be the functional equivalent fertilin α in humans.[5]
In common with other ADAM family members, ADAM20 contains a N-terminal reprolysin family propeptide (residues 57–159), reprolysin (M12B) family zinc metalloprotease domain (207–395), disintegrin domain (416–488), and a C-terminal ADAM cysteine-rich domain (493–605).[7]
The propeptide acts both a signal peptide and an activator domain. This prodomain has a cysteine that interacts with a zinc in the catalytic domain, thereby preventing the catalytic activity of the protein.When the pro-protein domain is cleaved, this cysteine zinc bond is broken and the protein is activated.[8] A notable variant showed an amino acid difference in the pro protein domain that prevented the cleavage of this domain which prevented the fusion of the sperm cell to an egg.[9]
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Hooft van Huijsduijnen R (January 1998). "ADAM 20 and 21; two novel human testis-specific membrane metalloproteases with similarity to fertilin-alpha". Gene. 206 (2): 273–82. doi:10.1016/s0378-1119(97)00597-0. PMID9469942.