A broad-spectrum family GH13 α-glucosidase from Marinovum sp., a member of the Roseobacter clade

Glycoside hydrolases (GHs) are a diverse group of enzymes that catalyze the hydrolysis of glycosidic bonds. The Carbohydrate-Active enZymes (CAZy) database organizes GHs into families based on sequence data and function, with fewer than 1% of the predicted proteins characterized biochemically. Consideration of genomic context can provide a useful guide to infer possible enzyme activities for proteins of unknown function. We used the MultiGeneBLAST tool to discover a putative gene cluster in Marinovum sp., a member of the marine Roseobacter clade, that encodes homologues of enzymes belonging to the sulfoquinovose monooxygenase pathway. This putative gene cluster lacks a gene encoding a classical family GH31 sulfoquinovosidase (SQase) candidate, but which instead includes an uncharacterized family GH13 protein ( Ms GH13). We show that recombinant Ms GH13 lacks SQase activity but is a broad spectrum α-glucosidase active on a diverse array of α-linked disaccharides, including: maltose (100%), sucrose (7.9%), nigerose (52%), trehalose (20%), isomaltose (6.4%), and kojibiose (3.8%). Using AlphaFold, a 3D model for the MsGH13 enzyme was constructed that predicted its active site shared close similarity with a narrower specificity α-glucosidase from Halomonas sp. H11 of the same GH13 subfamily. This study supports recent findings that bacteria belonging to the Roseobacter clade can metabolize SQ without a classical SQase encoded in their genomes. ### Competing Interest Statement The authors have declared no competing interest.