|PDB structures||RCSB PDB PDBe PDBsum|
Polygalacturonase (EC 18.104.22.168, pectin depolymerase, pectinase, endopolygalacturonase, pectolase, pectin hydrolase, pectin polygalacturonase, endo-polygalacturonase, poly-alpha-1,4-galacturonide glycanohydrolase, endogalacturonase, endo-D-galacturonase, poly(1,4-alpha-D-galacturonide) glycanohydrolase, PG) is an enzyme produced in plants which is involved in the ripening process, and by some bacteria and fungi which are involved in the rotting process. PGs degrades polygalacturonan present in the cell walls of plants by hydrolysis of the glycosidic bonds that link galacturonic acid residues. Polygalacturonan is a significant carbohydrate component of the pectin network that comprises plant cell walls. The activity of the endogenous plant PGs work to soften and sweeten fruit during the ripening process. Similarly, phytopathogens use PGs as a means to weaken the pectin network, so that a host of digestive enzymes can be excreted into the plant host to acquire nutrients.
X-ray crystallography has been used to determine the three-dimensional structure of several PGs. Fungal PGs from Collectotrichum lupine, Aspergillus aculeatus, and Aspergillus niger (PG1 and PG2) have been crystallized. The PG from Erwinia carotovora is the crystallized bacterial PG. Because of the significant role PGs play in agriculture and industry, computational molecular modeling has been applied to generate theoretical structures of other important PGs. The experimentally determined crystal structures are used as templates for the computational threading process.
Most plants have inhibitor proteins against some PGs. The polygalacturonase inhibitor proteins (PGIPs) are leucine-rich repeat proteins that have been reported to demonstrate both competitive and non-competitive inhibition of PGs. The crystal structure has been determined for one plant PGIP, PGIP2 from Phaseolus vulgaris (bean). The theoretical structures of other PGIPs have been determined for some other common crops, using PGIP2 as the template.
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