Accepted name: 4-hydroxybutanoyl-CoA dehydratase
Reaction: 4-hydroxybutanoyl-CoA = (E)-but-2-enoyl-CoA + H2O
Glossary: 4-hydroxybutanoyl-CoA = 4-hydroxybutyryl-CoA
(E)-but-2-enoyl-CoA = crotonyl-CoA
Systematic name: 4-hydroxybutanoyl-CoA hydro-lyase
Comments: Contains FAD and a [4Fe-4S] iron-sulfur cluster. The enzyme has been characterized from several microorganisms, including Clostridium kluyveri, where it participates in succinate fermentation [1,2], Clostridium aminobutyricum, where it participates in 4-aminobutyrate degradation [3,4], and Metallosphaera sedula, where it participates in the 3-hydroxypropionate/4-hydroxybutyrate cycle, an autotrophic CO2 fixation pathway found in some thermoacidophilic archaea [5].
1.  Bartsch, R.G. and Barker, H.A. A vinylacetyl isomerase from Clostridium kluyveri. Arch. Biochem. Biophys. 92 (1961) 122–132. [PMID: 13687513]
2.  Scherf, U., Sohling, B., Gottschalk, G., Linder, D. and Buckel, W. Succinate-ethanol fermentation in Clostridium kluyveri: purification and characterisation of 4-hydroxybutyryl-CoA dehydratase/vinylacetyl-CoA Δ32-isomerase. Arch. Microbiol. 161 (1994) 239–245. [PMID: 8161284]
3.  Scherf, U. and Buckel, W. Purification and properties of an iron-sulfur and FAD-containing 4-hydroxybutyryl-CoA dehydratase/vinylacetyl-CoA Δ32-isomerase from Clostridium aminobutyricum. Eur. J. Biochem. 215 (1993) 421–429. [PMID: 8344309]
4.  Muh, U., Cinkaya, I., Albracht, S.P. and Buckel, W. 4-Hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum: characterization of FAD and iron-sulfur clusters involved in an overall non-redox reaction. Biochemistry 35 (1996) 11710–11718. [PMID: 8794752]
5.  Berg, I.A., Kockelkorn, D., Buckel, W. and Fuchs, G. A 3-hydroxypropionate/4-hydroxybutyrate autotrophic carbon dioxide assimilation pathway in Archaea. Science 318 (2007) 1782–1786. [PMID: 18079405]
[EC created 2009]
Accepted name: 4-hydroxybutyrate—CoA ligase (AMP-forming)
Reaction: ATP + 4-hydroxybutanoate + CoA = AMP + diphosphate + 4-hydroxybutanoyl-CoA
Other name(s): 4-hydroxybutyrate-CoA synthetase (ambiguous); 4-hydroxybutyrate:CoA ligase (ambiguous); hbs (gene name); 4-hydroxybutyrate—CoA ligase
Systematic name: 4-hydroxybutanoate:CoA ligase (AMP-forming)
Comments: Isolated from the archaeon Metallosphaera sedula. Involved in the 3-hydroxypropanoate/4-hydroxybutanoate cycle. cf. EC, 4-hydroxybutyrate—CoA ligase (ADP-forming).
1.  Ramos-Vera, W.H., Weiss, M., Strittmatter, E., Kockelkorn, D. and Fuchs, G. Identification of missing genes and enzymes for autotrophic carbon fixation in crenarchaeota. J. Bacteriol. 193 (2011) 1201–1211. [PMID: 21169482]
2.  Hawkins, A.S., Han, Y., Bennett, R.K., Adams, M.W. and Kelly, R.M. Role of 4-hydroxybutyrate-CoA synthetase in the CO2 fixation cycle in thermoacidophilic archaea. J. Biol. Chem. 288 (2013) 4012–4022. [PMID: 23258541]
[EC created 2014, modified 2019]
Accepted name: 4-hydroxybutyrate—CoA ligase (ADP-forming)
Reaction: ATP + 4-hydroxybutanoate + CoA = ADP + phosphate + 4-hydroxybutanoyl-CoA
Other name(s): Nmar_0206 (locus name)
Systematic name: 4-hydroxybutanoate:CoA ligase (ADP-forming)
Comments: The enzyme, characterized from the marine ammonia-oxidizing archaeon Nitrosopumilus maritimus, participates in a variant of the 3-hydroxypropanoate/4-hydroxybutanate CO2 fixation cycle. cf. EC, 4-hydroxybutyrate—CoA ligase (AMP-forming).
1.  Konneke, M., Schubert, D.M., Brown, P.C., Hugler, M., Standfest, S., Schwander, T., Schada von Borzyskowski, L., Erb, T.J., Stahl, D.A. and Berg, I.A. Ammonia-oxidizing archaea use the most energy-efficient aerobic pathway for CO2 fixation. Proc. Natl. Acad. Sci. USA 111 (2014) 8239–8244. [PMID: 24843170]
[EC created 2019]