An Unusual His/Asp Dyad Operates Catalysis in Agar-Degrading Glycosidases.

ABSTRACT: Agarose motifs, found in agars present in the cell walls of red algae, consist of alternating units of d-galactose (G) and α-3,6-anhydro-l-galactose (LA). Glycoside hydrolases from family 117 (GH117) cleave the terminal α-1,3-glycosidic bonds, releasing LA units. Structural studies have suggested that these enzymes use unconventional catalytic machinery, involving a histidine (His302) as a general acid rather than a carboxylic residue as in most glycosidases. By means of quantum mechanics/molecular mechanics metadynamics, we investigated the reaction mechanism of Phocaeicola plebeius GH117, confirming the catalytic role of His302. This residue shares a proton with a neighbor aspartate residue (Asp320), forming a His/Asp dyad. Our study also reveals that, even though the sugar unit a

SUBMITTER: Sagiroglugil M 

PROVIDER: S-EPMC11574756 | biostudies-literature | 2024 Nov

REPOSITORIES: biostudies-literature