EFFECT OF ENZYMATIC AND CHEMICAL DEGLYCOSYLATION ON PHYSICOCHEMICAL PROPERTIES OF GLUCOAMYLASE FROM ASPERGILLUS-AWAMORI X100 D27/

Glucoamylase from Aspergillus awamori, a glycoprotein containing two N -glycosyl-linked and 46 short O-glycosyl-linked carbohydrate chains pe r protein molecule, was studied by enzymatic deglycosylation. The O-gl ycosyl-linked component was modified with alpha-mannosidase, and the N -glycosyl-linked component was detached with endo-beta-N-acetylglucosa minidase F. The carbohydrate moiety was also chemically modified with NaIO4 and trifluoromethanesulfonic acid. Deglycosylation of the protei n reduces its stability and resistance to the secretory proteinase of the fungus. The conformational changes caused by deglycosylation sugge st a substantial contribution of the O-glycosyl-linked carbohydrate co nstituent to the stabilization of the domain structure of the glucoamy lase. The carbohydrate moiety was modified by increasing the extent of protein glycosylation using mannojirimycin, an inhibitor of alpha-man nosidases involved in protein processing. This modification noticeably increased the stability of the enzyme.