Reaction: Hydrolysis of β-D-galactopyranose-(1→4)-α-L-galactopyranose-6-sulfate linkages in porphyran
Other name(s): porphyranase; PorA; PorB; endo-β-porphyranase
Systematic name: porphyran β-D-galactopyranose-(1→4)-α-L-galactopyranose-6-sulfate 4-glycanohydrolase
Comments: The backbone of porphyran consists largely (~70%) of (1→3)-linked β-D-galactopyranose followed by (1→4)-linked α-L-galactopyranose-6-sulfate [the other 30% are mostly agarobiose repeating units of (1→3)-linked β-D-galactopyranose followed by (1→4)-linked 3,6-anhydro-α-L-galactopyranose] [2]. This enzyme cleaves the (1→4) linkages between β-D-galactopyranose and α-L-galactopyranose-6-sulfate, forming mostly the disaccharide α-L-galactopyranose-6-sulfate-(1→3)-β-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 [1]. Methylation of the D-galactose prevents the enzyme from Zobellia galactanivorans, but not that from Wenyingzhuangia fucanilytica, from binding at subsite -1 [2,3].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
References:
1. Hehemann, J.H., Correc, G., Barbeyron, T., Helbert, W., Czjzek, M. and Michel, G. Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature 464 (2010) 908-912. [PMID: 20376150]
2. Correc, G., Hehemann, J.H., Czjzek, M. and Helbert, W. Structural analysis of the degradation products of porphyran digested by Zobellia galactanivorans β-porphyranase A. Carbohydrate Polymers 83 (2011) 277-283.
3. Zhang, Y., Chang, Y., Shen, J., Mei, X. and Xue, C. Characterization of a novel porphyranase accommodating methyl-galactoses at its subsites. J. Agr. Food Chem. 68 (2020) 7032–7039. [PMID: 32520542]