<p> Members of this family represent the alpha subunit of the multifunctional enzyme complex of the fatty acid degradation cycle. Activities include: enoyl-CoA hydratase (<db_xref db="EC" dbkey="4.2.1.17"/>), dodecenoyl-CoA delta-isomerase activity (<db_xref db="EC" dbkey="5.3.3.8"/>), 3-hydroxyacyl-CoA dehydrogenase (<db_xref db="EC" dbkey="1.1.1.35"/>) and 3-hydroxybutyryl-CoA epimerase (<db_xref db="EC" dbkey="5.1.2.3"/>). A representative is <taxon tax_id="562">Escherichia coli</taxon> FadB (<db_xref db="SWISSPROT" dbkey="P21177"/>). This entry excludes the FadJ family represented by <db_xref db="SWISSPROT" dbkey="P77399"/>.</p>