Deglycosylation of .alpha.1-proteinase inhibitor by endo-.beta.-N-acetylglucosaminidase F

Abstract

The glycosidase endo-.beta.-N-acetylglucosaminidase F (endo F) from Flavobracterium meningosepticum was used for the deglycosylation of rat .alpha.1-proteinase inhibitor (.alpha.1PI). .alpha.1PI containing three oligosaccharide side chains of the complex type was isolated from rat serum or from the medium of rat hepatocyte primary cultures. High-mannose-type .alpha.1 PI or hybride-type .alpha.1PI was isolated from the media of hepatocytes treated with 1-deoxymannojirimycin or swainsonine, respectively. The susceptibility of complex-type .alpha.1PI to endo F was studied in the presence of various detergents. 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate and octyl glucopyranoside turned out to be most effective. In the absence of detergents, digestion of .alpha.1PI with high concentrations of endo F and/or long times of incubation led to the formation of .alpha.1PI with one and two oligosaccharide side chains. In the presence of 0.5% octyl glucopyranoside, the major cleavage products were unglycosylated .alpha.1PI and .alpha.1PI carrying one carbohydrate side chain. In contrast to the complex-type .alpha.1PI, the high-mannose type can be totally degylcosylated by endo F even in the absence of detergents. The susceptibility of the hyhrid-type .alpha.1PI to endo F is between that of the complex and the high-mannose types.