PRODUCTION AND CHARACTERIZATION OF EXTRACELLULAR URONIC ACID-CONTAINING GLYCOPROTEINS FROM FUSARIUM-OXYSPORUM

Fusarium and Giberella species were found to secrete acidic polysaccha rides when grown in Czapex-Dox medium. Fusarium oxysporum showed the h ighest rate of secretion of acidic sugars into the growth medium. The acidic sugar-containing glycoprotein from F. oxysporum was purified fr om the culture filtrate to apparent homogeneity on ultracentrifugation analysis, by ammonium sulfate precipitation, Toyopearl HW-55 gel filt ration and charcoal chromatography. The purified acidic sugar-containi ng glycoprotein has a 10% protein content and a content of 40% acidic sugars as glucuronic acid, and the neutral sugars present in this glyc oprotein are mainly mannose, galactose, and glucose. The protein moiet y of the glycoprotein contains a high proportion of serine and threoni ne residues. Treatment of the glycoprotein with alkaline solution resu lted in an increase in absorbance at 241 nm, and alkaline borohydride treatment resulted in a marked decrease in the number of serine and th reonine residues. We conclude that the glycoprotein has O-linked sugar chains which are mainly attached to serine and threonine residues of the protein moiety. The primary structure of the acidic polysaccharide from F. oxysporum was analyzed mainly by NMR spectrometry. The main p arts of this polysaccharide have structures similar to those of uronic acid-containing polysaccharide from Fusarium sp. M7-1.