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pectin methylesterase inhibitor and related proteins Pectin methylesterase (PME; Pectinesterase; EC 3.1.1.11; CAZy class 8 of carbohydrate esterases) catalyzes the demethylesterification of homogalacturonans in the cell wall. Its activity is regulated by the proteinaceous PME inhibitor (PMEI) which inhibits PME and invertase through formation of a non-covalent 1:1 complex. Depending on the mode of demethylesterification, PMEI activity results in either loosening or rigidification of the cell wall. PMEI has been implicated in the regulation of fruit development, carbohydrate metabolism and cell wall extension. It may also be involved in inhibiting microbial pathogen PMEs. Thus, PMEI probably plays an important physiological role in PME regulation in plants, possessing several potential applications in a food-technological context. CIF (cell-wall inhibitor of beta-fructosidase from tobacco) is structurally similar to PMEI and these members are also included in this model. Comparison of the CIF/INV1 structure with the complex between PMEI/PME suggests a common targeting mechanism in PMEI and CIF. However, CIF and PMEI use distinct surface areas to selectively inhibit very different enzymatic scaffolds. |
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Jiyao W et al.(2023). "The conserved domain database in 2023.",