8fra
Mouse acidic mammalian chitinase, catalytic domain in complex with diacetylchitobiose at pH 5.60
Structural highlights
FunctionCHIA_MOUSE Degrades chitin and chitotriose. May participate in the defense against nematodes, fungi and other pathogens. Plays a role in T-helper cell type 2 (Th2) immune response. Contributes to the response to IL-13 and inflammation in response to IL-13. Stimulates chemokine production by pulmonary epithelial cells. Protects lung epithelial cells against apoptosis and promotes phosphorylation of AKT1. Its function in the inflammatory response and in protecting cells against apoptosis is inhibited by allosamidin, suggesting that the function of this protein depends on carbohydrate binding. Presence in saliva and gastric juice suggests a function as a digestive enzyme.[1] [2] [3] [4] Publication Abstract from PubMedChitin is an abundant biopolymer and pathogen-associated molecular pattern that stimulates a host innate immune response. Mammals express chitin-binding and chitin-degrading proteins to remove chitin from the body. One of these proteins, Acidic Mammalian Chitinase (AMCase), is an enzyme known for its ability to function under acidic conditions in the stomach but is also active in tissues with more neutral pHs, such as the lung. Here, we used a combination of biochemical, structural, and computational modeling approaches to examine how the mouse homolog (mAMCase) can act in both acidic and neutral environments. We measured kinetic properties of mAMCase activity across a broad pH range, quantifying its unusual dual activity optima at pH 2 and 7. We also solved high resolution crystal structures of mAMCase in complex with oligomeric GlcNAcn, the building block of chitin, where we identified extensive conformational ligand heterogeneity. Leveraging these data, we conducted molecular dynamics simulations that suggest how a key catalytic residue could be protonated via distinct mechanisms in each of the two environmental pH ranges. These results integrate structural, biochemical, and computational approaches to deliver a more complete understanding of the catalytic mechanism governing mAMCase activity at different pH. Engineering proteins with tunable pH optima may provide new opportunities to develop improved enzyme variants, including AMCase, for therapeutic purposes in chitin degradation. Structural characterization of ligand binding and pH-specific enzymatic activity of mouse Acidic Mammalian Chitinase.,Diaz RE, Ecker AK, Correy GJ, Asthana P, Young ID, Faust B, Thompson MC, Seiple IB, Van Dyken SJ, Locksley RM, Fraser JS bioRxiv [Preprint]. 2024 Mar 25:2023.06.03.542675. doi: , 10.1101/2023.06.03.542675. PMID:37398339[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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