-!- The backbone of porphyran consists largely (approximately 70%) of (1->3)-linked beta-D-galactopyranose followed by (1->4)-linked alpha- L-galactopyranose-6-sulfate (the other 30% are mostly agarobiose repeating units of (1->3)-linked beta-D-galactopyranose followed by (1->4)-linked 3,6-anhydro-alpha-L-galactopyranose). -!- This enzyme cleaves the (1->4) linkages between beta-D- galactopyranose and alpha-L-galactopyranose-6-sulfate, forming mostly the disaccharide alpha-L-galactopyranose-6-sulfate-(1->3)-beta-D- galactose, although some longer oligosaccharides of even number of residues are also observed. -!- Since the enzyme is inactive on the non-sulfated agarose portion of the porphyran backbone, some agarose fragments are also included in the products. -!- Methylation of the D-galactose prevents its binding at position -1.