Purification and characterization of a beta-N-acetylglucosaminidase from Octopus vulgaris. Determination of specificity by using 360-MHz 1H-NMR spectroscopy.

We have purified a beta-N-acetylglucosaminidase from the hepatopancreas of the octopus which we have called beta I. The enzyme was homogeneous as judged by Sephadex column chromatography, isoelectric focusing, non-denaturing gel electrophoresis at two different pH and with sodium dodecyl sulphate/polyacrylamide gel electrophoresis. The native protein has an apparent molecular weight of 120 000 and we can conclude that it is a tetramer made up of two alpha and two beta subunits with apparent Mr of 27 000 and 34 000, respectively. Using NMR spectroscopy we have examined the specificity of beta I and have established that the enzyme hydrolyses the beta 1,4 linkage of N-acetylglucosamine but at only a specific site of the substrates used, two glycopeptides isolated from ovalbumin. To our knowledge this is the first known exoglycosidase which has both linkage and site specificity.