title: Enhanced thermal stability of chemically deglycosylated human choriogonadotropin.
abstract: Exposure of aqueous solutions of native human choriogonadotropin (hCG), asialo-hCG (A-hCG), and chemically deglycosylated hCG (DG-hCG) to heat treatment revealed significant differences in their stability. Solutions of hCG and A-hCG were rapidly inactivated above 50 degrees C. On the other hand, solutions of DG-hCG were comparatively more stable under similar conditions as shown by the retention of significant receptor binding, immunological, and hormonal antagonistic activities. Heated solutions (100 degrees C) of hCG and A-hCG quickly lost their ability to enhance the fluorescence of the probe 1-anilino-8-naphthalenesulfonate (1,8-ANS) indicating dissociation into subunits. DG-hCG solutions were more stable in this respect suggesting significant preservation of conformational features required for the interaction with 1,8-ANS. Solutions of hCG and A-hCG which had been thermally denatured (100 degrees C, 10 min) required almost 48 h at 37 degrees C to regain complete ANS binding ability as well as receptor binding activity. Under the same conditions, heated solutions of DG-hCG completely regained these abilities in less than 2 h. A similar pattern was observed with acid (pH 2.0)-dissociated hCG, A-hCG, and DG-hCG. While heated solutions of hCG had no effect on the action of native hCG in vitro, heated DG-hCG solutions still retained their ability to antagonize the cyclic AMP accumulation or steroidogenesis induced by native hCG in rat interstitial cells. Thus, removal of carbohydrate residues (approximately 75% loss) from hCG renders the hormone more resistant to thermal denaturation.
mesh_terms: D000818:Animals; D006063:Chorionic Gonadotropin / Q000378:metabolism; D004355:Drug Stability; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008297:Male; D011489:Protein Denaturation; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D011974:Receptors, LH; D013737:Testis / Q000378:metabolism
chemical_list: D006063:Chorionic Gonadotropin; C034923:HCG, deglycosylated; D011956:Receptors, Cell Surface; D011974:Receptors, LH