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Uncharacterized subfamily of plant invertase/pectin methylesterase inhibitors This subfamily contains inhibitors similar to those of pectin methylesterase (PME; Pectinesterase; EC 3.1.1.11; CAZy class 8 of carbohydrate esterases) that catalyzes the demethylesterification of homogalacturonans in the cell wall, and cell-wall invertases (CWIs) that catalyze the hydrolytic cleavage of the disaccharide sucrose into glucose and fructose. The proteinaceous PME inhibitor (PMEI) inhibits PME and invertase through formation of a non-covalent 1:1 complex. Cell-wall inhibitor of beta-fructosidase from tobacco (CIF) interacts with CWI in a strictly pH-dependent manner, modulated between pH 4 and 6, with rapid dissociation at neutral pH mediated by structure rearrangement or surface charge pattern in the binding interface. Comparison of the CIF/INV1 structure with the complex between the structurally CIF-related pectin methylesterase inhibitor (PMEI) and pectin methylesterase indicates a common targeting mechanism in PMEI and CIF. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",