Substrate Selectivity in Aspergillus niger KU-8 Acid Phosphatase II Using Phosphoryl Oligosaccharides

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  The intracellular acid phosphatase II (ACPase II) produced by Aspergillus niger KU-8 preferentially dephosphorylates C-6 phosphate groups rather than C-3 phosphate groups of phosphoryl oligosaccharides. In this study, the kinetic parameters of ACPase II were measured. 3²-phosphoryl maltotriose and 6²-phosphoryl maltotriose, which differ only in the binding position of the phosphate group, were prepared and used as the substrates. The K_m for both substrates were similar. However, the k_cat value for the 6²-phosphoryl maltotriose was about three-fold of that for the 3²-phosphoryl maltotriose.