Biosynthetic pathway for P(3HB). P(3HB) is synthesized in a three-step pathway by the successive action of b-ketoacyl-CoA thiolase (PhbA), acetoacetyl-
CoA reductase (PhbB), and P(3HB) polymerase (PhbC). The three enzymes are encoded by the genes of the phbCAB operon. A promoter upstream of phbC transcribes
the complete operon.