Acetyl substitution of glucuronan influences glucuronan cleavage by GlyA from Sinorhizobium meliloti M5N1CS (NCIMB 40472)

The Sinorhizobium meliloti M5N1CS strain produces during fermentation a polyglucuronan and oligoglucuronans β-(1→4) linked and partially acetylated. Following the detection of unsaturated oligoglucuronans in the culture media, a glucuronan lyase (GlyA) associated to the S. meliloti M5N1CS has been identified. In this work, we have studied the degradation by Glya of glucuronans with different degree of substitution by acetate and characterized the oligoglucuronans obtained. We have determined that acetyl residues on glucuronan influence the susceptibility of glucuronan to cleavage by the specific lyase and that 2,3-di-O-Ac-GlcpA residues, closed to the cleavage site, limited the depolymerization of a purified glucuronan, while the degradation of a nascent polymer was not affected.