A Mucor pusillus mutant defective in asparagine-linked glycosylation w
as found in our stock cultures. This mutant, designated 1116, secreted
aspartic proteinase (MPP) in a less-glycosylated form than that secre
ted by the wild-type strain. Analysis of enzyme susceptibility, lectin
binding, and carbohydrate composition indicated that this mutant secr
eted three glycoforms of MPPs, one of which contained no carbohydrate;
the other two had truncated asparagine-linked oligosaccharide chains
such as Man(0 similar to 1)GlcNAc(2). Further analysis using oligosacc
haride processing inhibitors, such as castanospermine, 1-deoxynojirimy
cin and N-methyldeoxynojirimycin, suggested that MPPs in the mutant we
re glycosylated through a transfer of the truncated lipid-linked oligo
saccharides, Man(0 similar to 1)GlcNAc(2), to the MPP protein but not
through an aberrant processing. In addition, genetic studies with forc
ed primary heterokaryons indicated that the mutation in strain 1116 wa
s recessive.