Xylanase inhibitor I-like (IPR033868)

Short name: Xylanase_inhibitor_I-like

Overlapping homologous superfamilies

Domain relationships



Xylanase inhibitor-I (TAXI-I) is a member of potent TAXI-type inhibitors of fungal and bacterial GH11 xylanases [PMID: 11139386]. Plants developed a diverse battery of defense mechanisms in response to continual challenges by a broad spectrum of pathogenic microorganisms. Their defense arsenal includes inhibitors of cell wall-degrading enzymes, which hinder a possible invasion and colonization by antagonists. Xylanases of fungal and bacterial pathogens are the key enzymes in the degradation of xylan in the cell wall. Plants secrete proteins that inhibit these degradation glycosidases, including xylanase.

Surprisingly, TAXI-I displays structural homology with the pepsin-like family of aspartic proteases but is proteolytically nonfunctional, because one or more residues of the essential catalytic triad are absent. It is considered a non-peptidase homologue in peptidase family A1 (MEROPS identifer A01.974). The structure of TAXI-I in complex with Aspergillus niger xylanase, illustrates the ability of tight binding and inhibition with subnanomolar affinity and indicates the importance of the C-terminal end for the differences in xylanase specificity among different TAXI-type inhibitors [PMID: 15166216].

This domain is also found in basic 7S globulin (Bg7S) from soybean, which is structurally similar to xylanase inhibitor protein TAXI-I from wheat, but it lacks inhibitory activity against not only GH11 but also GH12 enzymes [PMID: 21457461].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
  • cd05489 (xylanase_inhibitor_I_like)