Polysaccharides have attracted much attention due to their interesting physico-chemical and also biological properties that are explored in food, cosmetic and pharmaceutical industries. GY785 exopolysaccharide (EPS) presenting an unusual structure is secreted by the deep-sea hydrothermal bacterium, Alteromonas infernus. Low-molecular weight (LMW) derivatives obtained by chemical depolymerization of the native high molecular weight (HMW) EPS were previously shown to exhibit biological properties similar to glycosaminoglycans (GAG). In the present study, in order to generate well defined derivatives with a better control of the depolymerization, an enzymatic approach was applied for the first time. Various commercially available enzymes were firstly screened for their depolymerizing activities, however none of them was able to degrade the polysaccharide. Enzymatic assays performed with A. infernus protein extracts have shown that bacterium produces by itself endogenous enzymes able to depolymerize its own EPS. The oligosaccharides released by the enzymes were analyzed and their structures allowed to assess that the protein extract contains several depolymerizing activities.