Hydrolytic activity of α-galactosidases against deoxy derivatives of p-nitrophenyl α-d-galactopyranoside
Section snippets
1. Introduction
Generally, different types of exo-glycosidases are distinguished on the basis of specificity for the glycon structure of their substrates, and their substrate specificities are expressed in their relative activities against substrates having various aglycons. Indications exist that the specificity of glycosidases for the glycon moiety of the substrate is not absolute. Several studies reported that weak hydrolytic reactions with deoxy analogs of the appropriate glycon were catalyzed by several d
Synthesis of deoxy substrates
The structures of PNP α-d-galactopyranoside (1) and of the newly synthesized deoxy derivatives (7, 16, 23, and 27, Scheme 1) used in the present study are compared in Fig. 1. Each derivative, namely PNP 2-deoxy-α-d-lyxo-hexopyranoside (7), PNP 3-deoxy-α-d-xylo-hexopyranoside (16), PNP 4-deoxy-α-d-xylo-hexopyranoside (23), and PNP α-d-fucopyranoside (27), was obtained in crystalline form. The vicinal diaxial proton coupling constants (J2,3) observed in the 1H NMR spectra of 1, 7, 16, 23, and 27
Materials and methods
New compounds were characterized by elemental analysis and 1H NMR spectra. Melting points were determined with a Yamato model MP-21 capillary apparatus and are uncorrected. Optical rotations were measured with a Perkin–Elmer 141 polarimeter at 20 °C. 1H NMR spectra were recorded with a Varian VXR-400 spectrometer. Chemical shifts are expressed in ppm downfield shift from Me4Si. Mass spectra were obtained with a Jeol JMX SX-102A instrument under positive FAB conditions. Column chromatography was
Acknowledgements
The authors express their sincere thanks to Dr N. Miyata of the National Institute of Health Science for recording the 1H NMR spectra, Dr T. Nakata of the Institute of Physical and Chemical Research (RIKEN) for the elemental analysis, and Ms J. Nakate for the measurement of FAB mass spectra. This work was supported in part by Special Coordination Funds of the Science and Technology Agency of the Japanese Government.
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