Table 2.

Kinetic characteristics of P(3HB) biosynthetic enzymes

Enzyme and speciesKm(mM)SubstrateProductReference
Thiolase (condensation)
Z. ramigera0.33Acetyl-CoAAcetoacetyl-CoA35
Thiolase (thiolysis)
Z. ramigera0.024Acetoacetyl-CoAAcetyl-CoA35
0.46Acetoacetyl-pantheteineAcetyl-CoA + acetyl-pantheteine35
0.073Acetoacetyl-pantheteine-11-pivalateAcetyl-CoA + acetyl-pantheteine-11-pivalate35
(50%)a3-Ketovaleryl-CoAAcetyl-CoA + propionyl-CoA166
R. eutropha0.044Acetoacetyl-CoAAcetyl-CoA252
(3%)b3-Ketovaleryl-CoAAcetyl-CoA + propionyl-CoA252
(0%)b3-Ketohexanoyl-CoAAcetyl-CoA + butanoyl-CoA 252
NADPH-dependent reductase
Z. ramigera0.002Acetoacetyl-CoA3-Hydroxybutyryl-CoA198
0.0023-Ketovaleryl-CoA3-Hydroxyvaleryl-CoA198
0.0103-Ketohexanoyl-CoA3-Hydroxyhexanoyl-CoA198
0.99Acetoacetyl-pantheteine-11-pivalate3-Hydroxybutyryl-pantheteine-11-pivalate198
R. eutropha0.005Acetoacetyl-CoA3-Hydroxybutyryl-CoA252
(18%)b3-Ketovaleryl-CoA3-Hydroxyvaleryl-CoA252
(3.6%)b3-Ketohexanoyl-CoA3-Hydroxyhexanoyl-CoA252
P(3HB) polymerase
R. eutropha0.723-Hydroxybutyryl-CoAP(3HB)252
1.633-Hydroxyvaleryl-CoAPHV252
NDc3-Hydroxybutyryl-pantheteine-11-pivalateNone69
  • a Vmax with respect to acetoacetyl-CoA.

  • b Relative activity with respect to acetoacetyl-CoA and 3-hydroxybutyryl-CoA.

  • c ND, not determined.