This domain is found in porphyranase protein present in Bacteroides plebeius. Porphyranase breaks down porphyran during digestion of red seaweed glycans. It is worth noting that red seaweed glycans contain sulfate esters that are absent in terrestrial plants. This domain makes up part of the catalytic domain of the porphyranase protein [1].

1: Bacteria of the human gut microbiome catabolize red seaweed glycans with carbohydrate-active enzyme updates from extrinsic microbes. Hehemann JH, Kelly AG, Pudlo NA, Martens EC, Boraston AB; Proc Natl Acad Sci U S A. 2012;109:19786-19791. PMID:23150581