Inhibition of the rat clearance system for agalacto-orosomucoid by yeast mannans and by mannose

Abstract

Summary Infused asialo-orosomucoid, agalacto-orosomucoid and purified mannans from Saccharomyces cerevisiae are rapidly cleared from rat plasma. Clearance of 125 I-agalacto-orosomucoid is inhibited by simultaneously infused mannans and several simple sugars including mannose. Clearance of 125 I-mannans is inhibited by simultaneously infused agalacto-orosomucoid. Although mannans and agalacto-orosomucoid show cross-inhibition of clearance, neither inhibits the clearance of 125 I-asialo-orosomucoid. Thus, even though agalacto-orosomucoid is an N-acetylglucosamine terminal glycoprotein, a substantial part of its clearance from rat plasma is mediated by a mannose recognition system. Abbreviations Wild type mannan contains a 1→6 linked backbone with side chains of 1→3 and 1→2 linked mannose units. Mutant mannan mnn 2 (called 1→6 linked) has no 1→3 and 1→2 linked side chain on the polymannose backbone of the outer chain. Mannan from mutant mnn 1 (called 1→2 linked) has predominantly mannobiose side chains in 1→2 linkage. Mannan from mutant mnn 4 (called 1→3 linked) has many side chains with an additional mannose in 1→3 linkage