Effects of Unsaturated Uronic Acid Residues at Non-reducing End on Bond Cleavage Frequency of Poly(1,4-α-L-guluronide) Lyase from Enterobacter cloacae M-1.

The mode of action of poly(1,4-α-L-guluronide) lyase from Enterobacter cloacae M-1 on unsaturated oligoguluronic acids was studied using fluorophore-assisted carbohydrate electrophoresis. The polyguluronate lyase degraded unsaturated penta-, hexa-, and heptaguluronic acids, but not unsaturated oligoguluronic acids with DPs less than 4. On comparison with the aspect of enzymatic degradation of unsaturated oligoguluronic acid and saturated oligoguluronic acid having the same DP, the former was degraded faster than the latter, and also the cleavage pattern of the polyguluronate lyase on unsaturated oligoguluronic acids was considerably different from that on saturated oligoguluronic acids. From the results described above, we suggest that the affinity of the first subsite from the non-reducing end side of the enzyme to Δ residues is lower than that to GulA residues.