Superporodica cistatina obuhvata proteine koji sadrže višestruke sekvence slične cistatinu. Neki od članova su aktivni inhibitori cistein proteaza, dok su drugi izgubili ili možda nikada nisu stekli ovu inhibitornu aktivnost. U natporodici postoje tri porodice inhibitora, uključujući tip 1 cistatina (stefini), cistatini tipa 2 i kininogeni. Proteini cistatina tipa 2 su klasa inhibitora cistein-proteinaze koji se nalaze u raznim ljudskim tečnostima i sekretu. Lokus cistatina na hromosomu 20 sadrži većinu gena za cistatin tipa 2 i pseudogene. Ovaj gen nalazi se na telomernom kraju cistatinskog lokusa i kodira protein sličan cistatinu tipa 2. Specifična funkcija ovog proteina nije utvrđena.[5]
Thiesse M, Millar SJ, Dickinson DP (1994). "The human type 2 cystatin gene family consists of eight to nine members, with at least seven genes clustered at a single locus on human chromosome 20". DNA Cell Biol. 13 (2): 97–116. doi:10.1089/dna.1994.13.97. PMID8179826.
Dickinson DP, Zhao Y, Thiesse M, Siciliano MJ (1995). "Direct mapping of seven genes encoding human type 2 cystatins to a single site located at 20p11.2". Genomics. 24 (1): 172–5. doi:10.1006/geno.1994.1595. PMID7896273.
Dickinson DP, Thiesse M, Dempsey LD, Millar SJ (1993). "Genomic cloning, physical mapping, and expression of human type 2 cystatin genes". Crit. Rev. Oral Biol. Med. 4 (3–4): 573–80. doi:10.1177/10454411930040034401. PMID7690606.
Saitoh E, Isemura S, Sanada K, et al. (1989). "Cystatin superfamily. Evidence that family II cystatin genes are evolutionarily related to family III cystatin genes". Biol. Chem. Hoppe-Seyler. 369 Suppl: 191–7. PMID3202964.