The beta-1,4-endogalactanase A gene from Aspergillus niger is specifically induced on arabinose and galacturonic acid and plays an important role in the degradation of pectic hairy regions.
The Aspergillus nigerbeta-1,4-endogalactanase encoding gene (galA) was cloned and characterized. The expression of galA in A. niger was only detected in the presence of sugar beet pectin, d-galacturonic acid and l-arabinose, suggesting that galA is coregulated with both the pectinolytic genes as well as the arabinanolytic genes. The corresponding enzyme, endogalactanase A (GALA), contains both active site residues identified previously for the Pseudomonas fluorescensbeta-1,4-endogalactanase. The galA gene was overexpressed to facilitate purification of GALA. The enzyme has a molecular mass of 48.5 kDa and a pH optimum between 4 and 4.5. Incubations of arabinogalactans of potato, onion and soy with GALA resulted initially in the release of d-galactotriose and d-galactotetraose, whereas prolonged incubation resulted in d-galactose and d-galactobiose, predominantly. MALDI-TOF analysis revealed the release of l-arabinose substituted d-galacto-oligosaccharides from soy arabinogalactan. This is the first report of the ability of a beta-1,4-endogalactanase to release substituted d-galacto-oligosaccharides. GALA was not active towards d-galacto-oligosaccharides that were substituted with d-glucose at the reducing end.
De Vries
Ronald P
RP
Molecular Genetics of Industrial Microorganisms and Food Chemistry, Wageningen University, Wageningen, The Netherlands. r.p.devries@bio.uu.nl
Parenicová
Lucie
L
Hinz
Sandra W A
SW
Kester
Harry C M
HC
Beldman
Gerrit
G
Benen
Jacques A E
JA
Visser
Jaap
J
D000595:Amino Acid Sequence; D001089:Arabinose / Q000378:metabolism; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D002240:Carbohydrate Sequence; D003001:Cloning, Molecular; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D005685:Galactans / Q000737:chemistry / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006026:Glycoside Hydrolases; D006603:Hexuronic Acids / Q000378:metabolism; D006868:Hydrolysis; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D001616:beta-Galactosidase / Q000235:genetics* / Q000378:metabolism*
D005656:Fungal Proteins; D005685:Galactans; D006603:Hexuronic Acids; C007819:galacturonic acid; D001089:Arabinose; D006026:Glycoside Hydrolases; D001616:beta-Galactosidase; C094192:arabinogalactan endo-1,4-beta-galactosidase; C005653:arabinogalactan