4-hydroxybutanoate + ATP + CoA = 4-hydroxybutanoyl-CoA + AMP + diphosphate
4-hydroxybutanoate + atp + coa = 4-hydroxybutanoyl-coa + amp + diphosphate
"4-hydroxybutyrate--CoA ligase (AMP-forming)"
"4-hydroxybutyrate--coa ligase (amp-forming)"