The β-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.
de Vries, R. P., Pařenicová, L., Hinz, S. W. A., Kester, H. C. M., Beldman, G., Benen, J. A. E. & Visser, J. (2002). European Journal of Biochemistry, 269(20), 4985-4993.
The Aspergillus niger β-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 fluorescens β-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-galactooligosaccharides from soy arabinogalactan. This is the first report of the ability of a β-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.