ABSTRACT
Glycosylation, an important post-translation modification, could alter biological activity or influence the clearance rates of glycoproteins. We report here the first example of a heterozygous protein deficiency leading to metabolic alteration of N-glycan structures in residual secreted protein. Analysis of C1 esterase inhibitor (C1INH) glycans from normal individuals and patients with hereditary deficiency of C1INH demonstrated identical O-glycan structures but the N-glycans of patients with a heterozygous genetic deficiency were small, highly charged and lacked sialidase releasable N-acetylneuraminic acid. Structural studies indicate that the charge character of these aberrant N-glycan structures may result from the presence of mannose-6-phosphate residues. These residues might facilitate secretion of C1INH through an alternate lysosomal pathway, possibly serving as a compensatory mechanism to enhance plasma levels of C1INH in these deficient patients.
Subject(s)
Angioedema/genetics , Polysaccharides/chemistry , Polysaccharides/metabolism , Protein Deficiency/genetics , Serpins/metabolism , Angioedema/metabolism , Carbohydrate Conformation , Carbohydrate Sequence , Complement C1 Inactivator Proteins , Complement C1 Inhibitor Protein , Electrophoresis, Capillary , Electrophoresis, Polyacrylamide Gel , Glycosylation , Heterozygote , Humans , Molecular Sequence Data , N-Acetylneuraminic Acid/chemistry , N-Acetylneuraminic Acid/metabolism , Neuraminidase/metabolism , Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase/metabolism , Polysaccharides/genetics , Reference Values , Serpins/chemistry , Serpins/deficiency , Serpins/geneticsABSTRACT
The effect of dissolved oxygen concentration on human secreted alkaline phosphatase (SEAP) glycosylation by the insect cell-baculovirus expression system was investigated in a well-controlled bioreactor. Oligomannose-type N-linked glycans (i.e., Man2 to Man6 and Man3F) were present in SEAP produced by Spodoptera frusiperda Sf-9 (Sf-9) and Trichoplusia ni BTI-Tn-5B1-4 (Tn-5B1-4) insect cell lines. The relative amounts of the most highly processed glycans (i.e., Man3F and Man2 in the SEAP from Sf-9 and Tn-5B1-4 cells, respectively) were significantly higher at 50% of air saturation than at either 10% or 190% of air saturation. That is, glycan processing was inhibited at both low and high dissolved oxygen concentrations.
