Schizosaccharomyces pombe och1+ encodes α-1,6-mannosyltransferase that is involved in outer chain elongation of N-linked oligosaccharides

Abstract

The fission yeast Schizosaccharomyces pombe attaches an outer chain containing mannose and galactose to the N-linked oligosaccharides on many of its glycoproteins. We identified an S. pombe och1 mutant that did not synthesize the outer chains on acid phosphatase. The S. pombe och1+ gene was a functional homolog of Saccharomyces cerevisiae OCH1, and its gene product (SpOch1p) incorporated α-1,6-linked mannose into pyridylaminated Man9GlcNAc2, indicating that och1+ encodes an α-1,6-mannosyltransferase. Our results indicate that SpOch1p is a key enzyme of outer chain elongation. The substrate specificity of SpOch1p was different from that of S. cerevisiae OCH1 gene product (ScOch1p), suggesting that SpOch1p may have a wider substrate specificity than that of ScOch1p.