Subsite affinities of Aspergillus niger glucoamylase II determined with p-nitrophenylmaltooligosaccharides

Kinetic parameters were obtained for glucoamylase catalysed hydrolysis of substrates of an alpha-(1,4)-maltooligosaccharide series and of a p-nitro-phenyl-alpha-maltooligosaccharide series. p-Nitrophenyl substrates of chain length 11 and 17 were synthesized in 97% and 95% purity, respectively, to test the significance of binding at remote subsites. The affinities of the subsites > 4 are demonstrated to be insignificant. The subsite binding contributions for D-glucopyranosyl and for p-nitrophenyl residues were calculated.