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Characterization of the bga1 ‐encoded glycoside hydrolase family 35 β‐galactosidase of Hypocrea jecorina with galacto‐β‐ d ‐galactanase activity
Author(s) -
Gamauf Christian,
Marchetti Martina,
Kallio Jarno,
Puranen Terhi,
Vehmaanperä Jari,
Allmaier Günter,
Kubicek Christian P.,
Seiboth Bernhard
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.05714.x
Subject(s) - hypocrea , galactosides , trichoderma reesei , biochemistry , lactose , chemistry , galactose , isoelectric point , hydrolysis , enzyme , cellulase
The extracellular bga1 ‐encoded β‐galactosidase of Hypocrea jecorina ( Trichoderma reesei ) was overexpressed under the pyruvat kinase ( pki1 ) promoter region and purified to apparent homogeneity. The monomeric enzyme is a glycoprotein with a molecular mass of 118.8 ± 0.5 kDa (MALDI‐MS) and an isoelectric point of 6.6. Bga1 is active with several disaccharides, e.g. lactose, lactulose and galactobiose, as well as with aryl‐ and alkyl‐β‐ d ‐galactosides. Based on the catalytic efficiencies, lactitol and lactobionic acid are the poorest substrates and o ‐nitrophenyl‐β‐ d ‐galactoside and lactulose are the best. The pH optimum for the hydrolysis of galactosides is ∼ 5.0, and the optimum temperature was found to be 60 °C. Bga1 is also capable of releasing d ‐galactose from β‐galactans and is thus actually a galacto‐β‐ d ‐galactanase. β‐Galactosidase is inhibited by its reaction product d ‐galactose and the enzyme also shows a significant transferase activity which results in the formation of galacto‐oligosaccharides.