Inversion of configuration during hydrolysis of alpha-1,4-galacturonidic linkage by three Aspergillus polygalacturonases.
Endopolygalacturonases I and II (PGI and PGII) of Aspergillus niger and an exopolygalacturonase (ExoPG) of A. tubingensis were investigated to reveal the stereochemistry of their hydrolytic action. Reduced pentagalacturonic acid (pentaGalU-ol) and reduced trigalacturonic acid (triGalU-ol) were used as non-reducing substrates for the enzymes. The configuration of the reducing ends in the products formed in D2O reaction mixtures was followed by 1H-NMR spectroscopy. It has been unambiguously established that primary cleavage of pentaGalU-ol by both PGI and PGII leads to diGalU-ol and the beta-anomer of triGalUA. The primary products of hydrolysis of triGalUA-ol by ExoPG were diGal-ol and the beta-anomer of GalUA. Thus, all three Aspergillus polygalacturonases belong to the so-called inverting glycanases, i.e. they utilize the single displacement mechanism of hydrolysis of the glycosidic linkage.
Biely
P
P
Institute of Chemistry, Slovak Academy of Sciences, Slovak Republic.
Benen
J
J
Heinrichová
K
K
Kester
H C
HC
Visser
J
J
D001230:Aspergillus / Q000201:enzymology*; D001234:Aspergillus niger / Q000201:enzymology*; D002236:Carbohydrate Conformation; D006603:Hexuronic Acids / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D009844:Oligosaccharides / Q000378:metabolism; D011096:Polygalacturonase / Q000378:metabolism*; D013237:Stereoisomerism; D013400:Sugar Acids / Q000378:metabolism; D014312:Trisaccharides / Q000378:metabolism
D006603:Hexuronic Acids; D009844:Oligosaccharides; D013400:Sugar Acids; D014312:Trisaccharides; C096230:pentagalacturonic acid; C007819:galacturonic acid; C065008:O-galactopyranosyluronic acid-(1-4)-O-galactopyranosyluronic acid-(1-4)-galactopyranosyluronic acid; D011096:Polygalacturonase