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Tandem mass spectrometric analysis of Aspergillus niger pectin methylesterase: mode of action on fully methyl-esterified oligogalacturonates

2000; Portland Press; Volume: 346; Issue: 2 Linguagem: Inglês

10.1042/bj3460469

1470-8728

H.C.M. Kester, Jacques Benen, Jaap Visser, Maria Warren, Ron Orlando, Carl Bergmann, Didier Magaud, Daniel Anker, Alain Doutheau,

Microbial Metabolites in Food Biotechnology

The substrate specificity and the mode of action of Aspergillus niger pectin methylesterase (PME) was determined using both fully methyl-esterified oligogalacturonates with degrees of polymerization (DP) 2-6 and chemically synthesized monomethyl trigalacturonates. The enzymic activity on the different substrates and a preliminary characterization of the reaction products were performed by using high-performance anion-exchange chromatography at neutral pH. Electrospray ionization tandem MS (ESI-MS/MS) was used to localize the methyl esters on the 18O-labelled reaction products during the course of the enzymic reaction. A. niger PME is able to hydrolyse the methyl esters of fully methyl-esterified oligogalacturonates with DP 2, and preferentially hydrolyses the methyl esters located on the internal galacturonate residues, followed by hydrolysis of the methyl esters towards the reducing end. This PME is unable to hydrolyse the methyl ester of the galacturonate moiety at the non-reducing end.