Cell lines having genetically modified glycosylation pathways that allow
them to carry out a sequence of enzymatic reactions, which mimic the
processing of glycoproteins in humans, have been developed. Recombinant
proteins expressed in these engineered hosts yield glycoproteins more
similar, if not substantially identical, to their human counterparts. The
lower eukaryotes, which ordinarily produce high-mannose containing
N-glycans, including unicellular and multicellular fungi are modified to
produce N-glycans such as Man.sub.5GlcNAc.sub.2 or other structures along
human glycosylation pathways. This is achieved using a combination of
engineering and/or selection of strains which: do not express certain
enzymes which create the undesirable complex structures characteristic of
the fungal giycoproteins, which express exogenous enzymes selected either
to have optimal activity under the conditions present in the fungi where
activity is desired, or which are targeted to an organelle where optimal
activity is achieved, and combinations thereof wherein the genetically
engineered eukaryote expresses multiple exogenous enzymes required to
produce "human-like" glycoproteins.