Chemical deglycosylation (dg) of sturgeon Acipenser gueldenstaedti Br. (alphaGTH) resulted in the loss of 83% of its initial carbohydrate content. It altered also recombinant dgalphaGTH + betaGTH dimer molecule, reducing its immunoreactivity by 30%, and fully blocking the hormonal function. CD spectroscopy showed that deglycosylation led to changes in the secondary structure of dgalphaGTH and in the alpha-beta recombinant. The sugar moiety of sturgeon alphaGTH is suggested to play an important role in maintaining the biological function of the hormone dimer molecule.