Glycosylation heterogeneity of recombinant plasminogen expressed in CHO cells

Plasminogen (Plg) is the zymogen form of the serine protease plasmin and has been expressed In a CHO cell line. It is a prerequisite for such recombinant human glycoproteins being produced in mammalian cell systems that then glycosylation profile is similar to the native protein secreted by the human liver. Pig exists as true glycoforms, types I and II, type I having both an N-linked glycosylation site occupied at Asn(289) and an O-linked site at Thr(346). Type II is only modified at Thr(346), despite also containing tire N-linked consensus sequence. Capillary zone electrophoresis has been used to separate both glycoforms showing the relative distribution of both types in human plasminogen. Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-MS) has been used to determine the sugar structures on glycopeptides generated following chymotrypsin digestion of human Plg.