Action of galactanase from Penicillium citrinum on O-nitrophenyl-.BETA.-D-galactopyranoside.

The action of endo-l, 4-β-D-galactanase from Penicillium citrinum on o-nitrophenyl-β-Dgalactopyranoside (ONPG) was investigated. In reaction mixtures with various concentrations of ONPG, liberation of o-nitrophenol (ONP) was observed after a lag phase and then oligosaccharides with and without ONP-group were found to accumulate. The products were separated by activated carbon column chromatography and paper chromatography, and found to be a series of β-l, 4-linked galactooligosaccharides and their ONP-substituted derivatives. Liberation of ONP from the ONP-substituted oligosaccharides by the enzyme occured without a lag phase. Furthermore, the lag phase of ONP liberation from ONPG was eliminated by the addition ofβ-l, 4-galactotriose and -tetraose to the reaction mixture. The formation of ONP-substituted oligosaccharides before the liberation of ONP is assumed to be the cause of the observed lag.