Significant steroidogenic activity of luteinizing hormone is maintained after enzymatic removal of oligosaccharides

Abstract

Several reports have described the destruction of the N-linked oligosaccharides on glycoprotein hor-mones by hydrogen fluoride treatment and have noted the accompanying marked reduction, or com-plete loss, in biological activity. This has led to the concept that the oligosaccharides have an obliga-tory role in glycoprotein hormone steroidogenic function. Using a less radical and more complete method for removing sugar units, endoglycosidase treatment and ovine LH (oLH) and human LH (hLH) as examples, we examined the role of oligosaccha-rides in hormone function. Ovine LH and hLH were digested with endoglycosidase F. After treatment cleavage of oligosaccharides was demonstrated by compositional studies, greater than 87% cleavage was demonstrated and only N-acetylglucosamine or N-acetylglucosamine-Fucose shown to remain at-tached to the peptide, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (appropriate size change) and by chromatofocusing (appearance of a single basic peak). Biological activities and relative potencies of preparations were then as-sessed in an in vitro assay, in which the ability of samples to promote testosterone production by tes-ticular interstitial cells was measured. Although en-doglycosidase F treatment reduced relative poten-cies 2-to 3-fold in the bioassay, (possibly in part due to subunit dissociation) it did not lessen abilities to induce maximal testosterone response (that of native hLH and oLH). These findings contrast with those obtained from hydrogen fluoride studies and indicate that the oligosaccharides, per se, do not play an obligatory role in the steroidogenic activity of LH. © 1987 by The Endocrine Society.