The marine bacterium Saccharophagus degradans 2-40 produces a multi-component cellulolytic system proposed to consist of 10 annotated GH5 endoglucanases, two GH9 endoglucanases, one cellobiohydrolase, five glucosidases and two phosphorylases.  The S. degradans system is unusual in the abundance of GH5-containing cellulases and an apparent deficiency of processive enzymes.  Each of the 10 GH5 containing cellulases were cloned into pET28b and expressed in E. Coli Rossetta^TM.  After purification to near homogeneity, selected biochemical properties were assessed.  For each enzyme either the full-length enzyme or a degradation product sufficient to carry the catalytic domain exhibited cellulase activity, thus confirming their annotation as endoglucanases.   One cellulase, Cel5H, showed significantly greater activity on several cellulose substrates.  The activity of this enzyme primarily released cellobiose during short digestions and the ratio of soluble to insoluble products was greater than 4 irrespective of the length of digestion, consistent with processivity.  This activity resided with the catalytic domain and was found to be specific to amorphous cellulose.  The processivity coupled with viscosity reduction of Carboxymethyl cellulose solutions and synergisms with known cellulases argues that Cel5H is a processive endoglucanase.  Phylogenetic analyses indicated that Cel5H is a member of a separate clade of GH5-containing enzymes that also included Cel5G and Cel5J. These enzymes were also found to be processive endoglucanses whereas the other GH5 cellulases of S. degradans were classical endoglucanases.  Thus the S. degradans cellulolytic system utilizes novel GH5-containing processive endoglucanases to degrade cellulose.