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

The fission yeast Schizosaccharomyces pombe attaches an outer chain contain ing mannose and galactose to the N-linked oligosaccharides on many of its g lycoproteins, We identified an S. pombe och1 mutant that did not synthesize the outer chains on acid phosphatase. The S. pombe och1(+) gene was a func tional homolog of Saccharomyces cerevisiae OCH1, and its gene product (SpOc h1p) incorporated alpha -1,6-linked mannose into pyridylaminated Man(9)GlcN Ac(2), indicating that och1(+) encodes an alpha -1,6-mannosyltransferase. O ur results indicate that SpOch1p is a key enzyme of outer chain elongation. The substrate specificity of SpOch1p was different from that of S. cerevis iae OCH1 gene product (ScOch1p), suggesting that SpOch1p may have a wider s ubstrate specificity than that of ScOch1p. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserv ed.