지방산 생합성 축합 Acetyl-CoA가 카르복실화되면서 malonyl-CoA 합성 (acetyl-CoA carboxylase) CO2 + acetyl CoA + ATP + biotin-enz  malonyl CoA + biotin-enz + ADP + Pi 2) Malonyl-CoA  Malonyl-ACP (Malonyl transacylase) 3) Acetyl-ACP와 malonyl-ACP 축합반응  acetoacetyl-ACP 형성 (β-ketoacyl-ACP-synthase)

축합 4) Acetoacetyl-ACP  β-hydroxybutyryl-ACP (환원, NADPH + H+  NADP+ ) (β-ketoacyl-ACP reductase) 5) β-hydroxybutyryl-ACP  Crotonyl-ACP (탈수) (β-hydroxybutyryl-ACP dehydrogenase) 6) Crotonyl-ACP  Butyryl-ACP (transenoyl-ACP reductase) 7) Butyryl기는 β-ketoacyl -ACP-synthase로 전달되고 새롭게 유리된 ACP-SH기는 다른 말로닐기와 결합 이 과정의 반복 속에 결국 palmitoyl-ACP 생성 8) 지방산합성효소 thioesterase에 의해 palmitate가 생성

지방산 합성 Acetyl-CoA  malonyl-CoA (acetyl-CoA carboxylase) CO2 + acetyl CoA + ATP + biotin-enz  malonyl CoA + biotin-enz + ADP + Pi 2) Malonyl-CoA  Malonyl-ACP (Malonyl transacylase) 3) Acetyl-ACP + malonyl-ACP  acetoacetyl-ACP (축합, β-ketoacyl-ACP-synthase) 4) Acetoacetyl-ACP  β-hydroxybutyryl-ACP (환원, NADPH + H+  NADP+ ) (β-ketoacyl-ACP reductase) FIGURE 21-2 (part 1) Addition of two carbons to a growing fatty acyl chain: a four-step sequence. Each malonyl group and acetyl (or longer acyl) group is activated by a thioester that links it to fatty acid synthase, a multienzyme system described later in the text. 1 Condensation of an activated acyl group (an acetyl group from acetyl-CoA is the first acyl group) and two carbons derived from malonyl-CoA, with elimination of CO2 from the malonyl group, extends the acyl chain by two carbons. The mechanism of the first step of this reaction is given to illustrate the role of decarboxylation in facilitating condensation. The β-keto product of this condensation is then reduced in three more steps nearly identical to the reactions of β oxidation, but in the reverse sequence: 2 the β-keto group is reduced to an alcohol, 3 elimination of H2O creates a double bond, and 4 the double bond is reduced to form the corresponding saturated fatty acyl group.

지방산합성 5) β-hydroxybutyryl-ACP  Crotonyl-ACP (탈수) (β-hydroxybutyryl-ACP dehydrogenase) 6) Crotonyl-ACP  Butyryl-ACP (환원, NADPH + H+  NADP+ ) (transenoyl-ACP reductase) 7) Butyryl기는 β-ketoacyl-ACP-synthase로 전달되고 새롭게 유리된 ACP-SH기는 다른 말로닐기와 결합 이 과정의 반복 속에 결국 palmitoyl-ACP 생성 8) 지방산합성효소 thioesterase에 의해 palmitate가 생성 FIGURE 21-2 (part 2) Addition of two carbons to a growing fatty acyl chain: a four-step sequence. Each malonyl group and acetyl (or longer acyl) group is activated by a thioester that links it to fatty acid synthase, a multienzyme system described later in the text. 1 Condensation of an activated acyl group (an acetyl group from acetyl-CoA is the first acyl group) and two carbons derived from malonyl-CoA, with elimination of CO2 from the malonyl group, extends the acyl chain by two carbons. The mechanism of the first step of this reaction is given to illustrate the role of decarboxylation in facilitating condensation. The β-keto product of this condensation is then reduced in three more steps nearly identical to the reactions of β oxidation, but in the reverse sequence: 2 the β-keto group is reduced to an alcohol, 3 elimination of H2O creates a double bond, and 4 the double bond is reduced to form the corresponding saturated fatty acyl group.