Pathway V uses succinic semialdehyde dehydrogenase (SucD), 4-hydroxybutyrate
dehydrogenase (4hbD), and 4-hydroxybutyrate-CoA:CoA transferase (OrfZ) to
synthesize 4-hydroxybutyryl-CoA for forming 4-hydroxybutyrate-containing PHA.
Pathway V was reported in Clostridium kluyveri (Valentin and Dennis 1997).