Cleaves the sulfated polysaccharide porphyran at 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. Some longer oligosaccharides of even number of residues are also observed. Inactive on the non-sulfated agarose portion of the porphyran backbone. Hydrolysis of beta-D-galactopyranose-(1->4)-alpha-L-galactopyranose-6-sulfate linkages in porphyran. Gut bacteria supply the human body with energy from dietary polysaccharides through glycosidases that are absent in the human genome. Beta-porphyranases, which are active on sulfated polysaccharides from marine red algae of the genus Porphyra, are present in marine bacteria. They are absent from metagenome data of gut bacteria, except from the genome of the gut bacterium B.plebeius isolated from Japanese individuals. Seaweeds make an important contribution to the diet in Japan and Porphyra (nori) is the most important nutritional seaweed used to prepare sushi, suggesting that seaweeds with associated marine bacteria have been the route by which genes coding for beta-porphyranases have been transferred in human gut B.plebeius genome (PubMed:20376150 and PubMed:23150581). Belongs to the glycosyl hydrolase 16 family. A gut's tale - Issue 158 of March 2014