Proteinase inhibitor I1, Kazal-type, metazoa (IPR001239)

Short name: Prot_inh_Kazal-m

Overlapping homologous superfamilies

Family relationships



This family of Kazal eukaryotic proteinase inhibitors, belongs to MEROPS inhibitor family I1, clan IA. They inhibit serine peptidases of the S1 family (IPR001254) [PMID: 14705960]. They are restricted to the metazoa (arthropoda and chordata), and includes a single exception in the alveolata (apicomplexa). No members are found in nematodes, fungi or plants.

Kazal inhibitors, which inhibit a number of serine proteinases (such as trypsin and elastase), belong to family of proteins that includes pancreatic secretory trypsin inhibitor; avian ovomucoid; acrosin inhibitor; and elastase inhibitor. These proteins contain between 1 and 7 Kazal-type inhibitor repeats [PMID: 6699915, PMID: 3828298].

The structure of the Kazal repeat includes a large quantity of extended chain, 2 short alpha-helices and a 3-stranded anti-parallel beta sheet [PMID: 6699915].The inhibitor makes 11 contacts with its enzyme substrate: unusually, 8 of these important residues are hypervariable [PMID: 3828298]. Altering the enzyme-contact residues, and especially that of the active site bond, affects the the strength of inhibition and specificity of the inhibitor for particular serine proteinases [PMID: 3828298, PMID: 7046785].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004867 serine-type endopeptidase inhibitor activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.