The following class of molecule is disclosed: a dimer containing a first neublastin polypeptide and a second neublastin polypeptide, wherein: (a) at least one of the polypeptides is glycosylated; (b) at least one of the polypeptides is conjugated at its N-terminus to a water-soluble synthetic polymer; and (c) neither of the polypeptides is conjugated to a water-soluble synthetic polymer at a position other than the N-terminus. Such dimers possess the biological activity of wild-type neublastin while displaying enhanced serum half-life and enhanced potency relative to wild-type neublastin.