A widespread family of oxidoreductive sulfoquinovosidases at the gateway to sulfoquinovose catabolism

09 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The sulfosugar sulfoquinovose (SQ) is produced by photosynthetic plants, algae and cyanobacteria on a scale of 10 billion tonnes per annum. Its degradation, which is essential to allow cycling of its constituent carbon and sulfur, involves specialized glycosidases termed sulfoquinovosidases (SQases), which release SQ from sulfolipid glycoconjugates so it can enter SQ catabolism pathways. However, many SQ catabolic gene clusters lack a gene encoding a classical SQase. Here, we report the discovery of a new family of SQases that use an atypical oxidoreductive mechanism involving NAD+ as a catalytic cofactor. 3D X-ray structures of complexes with SQ and NAD+ provide insight into the catalytic mechanism, which involves transient oxidation at C3. Bioinformatic survey reveals this new family of NAD-dependent SQases occur within sulfoglycolytic and sulfolytic gene clusters that lack classical SQases, and are distributed widely including within Roseobacter clade bacteria, suggesting an important contribution to marine sulfur cycling.


biological sulfur cycle
glycoside hydrolase
plant sulfolipid
structural biology
catalytic mechanism

Supplementary materials

Supporting information
Detailed experimental procedures, supplementary Figures and Tables: Figures S1-S16, Tables S1-S3 (PDF).


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