Work

The [FeFe]-hydrogenase So HydAB of Shewanella oneidensis – An Atypical M2(D)-type Enzyme that Drives Formate Oxidation

Year: 2026

Type: preprint

Abstract: The gamma-proteobacterium Shewanella oneidensis harbours one [NiFe]- and one [FeFe]-hydrogenase. This paper presents the first biochemical characterisation of So HydAB, a M2(D)-type [FeFe]-hydrogenase consisting of a small subunit featuring a twin-arginine-targeting motif (TAT) and a large subunit harbouring the active site cofactor and two accessory iron-sulfur clusters. There are three main reasons to investigate this enzyme. Firstly, S. oneidensis is a highly studied, metabolically complex, and widely utilised organism, especially in the context of wastewater treatment, CO 2 conversion, and microbial fuel cells, including H 2 -producing systems. Advanced understanding of its hydrogen metabolism can improve biotechnological applications. Secondly, S. oneidensis has been a mainstay of hydrogenase research for decades as its enzymes HydE, F and G are the most widely studied and utilised maturases – enzymes assembling the active site cofactor of [FeFe]-hydrogenases. Lastly, while enzymes like Nd HydAB from Nitratidesulfovibrio vulgaris (formerly Dd HydAB, Desulfovibrio vulgaris ) with high similarity to So HydAB have been characterised extensively in the past, the metabolic context of the enzyme in Shewanella is different from Nitratidesulfovibrio . While Nd HydAB receives electrons from ferredoxin, So HydAB accepts electrons from the menaquinone pool of the outer membrane while being a soluble enzyme in the periplasm. This is facilitated by interaction with a membrane-integrated cytochrome b transcribed from the same operon. Oxidation of the menaquinone pool drives oxidation of formate toward CO 2 via formate dehydrogenase. This study therefore lays the groundwork for understanding H 2 -dependent CO 2 turnover, a new type of metabolic niche for [FeFe]-hydrogenases, while simultaneously improving our understanding of a widely used platform organism.

Source: bioRxiv (Cold Spring Harbor Laboratory)

DOI: 10.64898/2026.10.15.759383

Authors: Florian Riemer, Max A. Klamke, Anna-Maria Wandinger, Thomas Happe, Sven T. Stripp, Eckhard Hofmann

Institutions: Ruhr University Bochum, University of Potsdam

Language: English

Topic: Metalloenzymes and iron-sulfur proteins

Subfield: Biochemistry

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Affordable and clean energy

Open Access status: green

Funder: Deutsche Forschungsgemeinschaft