A broad-spectrum α-glucosidase of glycoside hydrolase family 13 fromMarinovumsp., a member of theRoseobacterclade

Abstract

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 inMarinovumsp., a member of the marineRoseobacterclade, 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 (MsGH13). We show that recombinantMsGH13 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 fromHalomonassp. H11 of the same GH13 subfamily. This study supports recent findings that bacteria belonging to theRoseobacterclade can metabolize SQ without a classical SQase encoded in their genomes.