Structures of Galactose-Containing Oligosaccharides of α-Mannosidase from Porcine Kidney

Abstract

Oligosaccharides of a non-oligomannoside type were released from porcine α-mannosidase by hydrazinolysis, and were fractionated into at least 15 homogeneous oligosaccharides. Most of them are oligosaccharides with galactose and N-acetyl-glucosamine residues attached to a common core, αMan₂βManβGlcNAc(±α-L-Fuc)βGlcNAc. About 50% of the oligosaccharides contain one or two outer chains composed of one β-linked N-acetylglucosamine and two β-linked galactose residues attached to the core portions, and the others seem to be metabolic inter-mediates. Based on the results of studies on the binding of α-mannosidase to RCA (Ricinus communis agglutinin) I-agarose and MBP (mannan-binding protein)-Se-pharose, which are specific for glycoproteins possessing N-acetyllactosamine-type and oligomannoside-type (including oligomannosides with N-acetylglucosamine at the reducing termini) oligosaccharides, respectively, about 85% of the enzyme molecules were found to have both types of oligosaccharides. Similarly, it was shown that of the several acid hydrolases present in the lysosomes purified from rat liver, only α-mannosidase has both types of oligosaccharides, and the greater parts of β-glucuronidase, acid phosphatase and β-N-acetylhexosaminidase seem to have only oligomannoside-type oligosaccharides.