N-glycosylated variants of growth hormone in human pituitary extracts

This study was designed to investigate the existence, in human pituitary extracts, of growth hormone (GH) variants not encoded by the hGH-N gene. Using anion exchange-fast protein liquid chromatography followed by SDS-PAGE, we isolated several basic forms of pituitary GH. Incubation of these basic forms with endoglycosidase F/N-glycosidase F revealed that two of them (about 34 and 12 kD) were N-glycosylated. In contrast, no changes were found when samples were incubated with the O-linked glycosylation-specific O-glycosidase. Since the GH-N molecule lacks consensus sequences for N-linked glycosylation, our findings suggest that GH genes other than hGH-N are expressed in the human pituitary gland.