InterPro domain: IPR030664

Adenylylsulphate (APS) reductase catalyses reversibly the two-electron reduction of APS to sulphite and AMP during dissimilatory sulphate reduction or sulphur oxidation. Found in several bacterial lineages and in Archaeoglobales, APS reductase is a heterodimer composed of an alpha subunit containing a noncovalently bound FAD, and a beta subunit containing two [4Fe-4S] clusters. The alpha subunit of APS reductase shares a common evolutionary origin with fumarate reductase/succinate dehydrogenase flavoproteins [ 1 ].

Two distinct, membrane-bound, FAD-containing enzymes are responsible for the catalysis of fumarate and succinate interconversion; the fumarate reductase is used in anaerobic growth, and the succinate dehydrogenase is used in aerobic growth [ 2 ]. Succinate dehydrogenase (Sdh), a primary respiratory dehydrogenase, catalyses electron transfer from succinate to membrane-bound quinone. Fumarate reductase (Frd) catalyses the opposite reaction.

The enzyme complex consists at least of four subunits. The hydrophilic catalytic domain consists of a flavoprotein that contains covalently bound FAD and an active site of the enzyme [ 3 , 4 ].

1. Adenylylsulfate reductases from archaea and bacteria are 1:1 alphabeta-heterodimeric iron-sulfur flavoenzymes--high similarity of molecular properties emphasizes their central role in sulfur metabolism. FEBS Lett. 473, 63-6
2. Anaerobic expression of Escherichia coli succinate dehydrogenase: functional replacement of fumarate reductase in the respiratory chain during anaerobic growth. J. Bacteriol. 180, 5989-96
3. Identification of the covalently bound flavin of succinate dehydrogenase as 8-alpha-(histidyl) flavin adenine dinucleotide. J. Biol. Chem. 245, 4224-5
4. The sequence of the flavoprotein subunit of bovine heart succinate dehydrogenase. J. Biol. Chem. 267, 11553-8