HSCH3-C(2)装载SKSMTACPKRAT丙二酸单酰基加载于ACP-磷HDER酸泛酸统基乙胺的-SH上。合成丙二酸单酰-ACP。0CCH2S-CoA+CoA-SHMTOCH2-C-SC-丙二酸单酰基转移反应：OCH3-CE2 (MT) :C丙二酸单酰CoA:ACP转酰酶KSMTFattyacid synthaseACPKRATcomplex chargedHDwithanacetylandERamalonyl group丙二酸单酰CoA+ACP-SH一丙二酸单酰-S-ACP+CoASH
MT (2)装载 丙二酸单酰基转移反应： E2（MT）： 丙二酸单酰CoA:ACP转酰酶 丙二酸单酰CoA + ACP-SH 丙二酸单酰-S-ACP + CoASH 丙二酸单酰基加载于ACP-磷 酸泛酸巯基乙胺的-SH上， 合成丙二酸单酰-ACP
Malonyl-CoA(3)缩合反应00CH26CS一0CHaCCSOMTKSACPKRATFattyacidsynthasecomplex chargedHDERwith an acetyl andamalonyl groupKS :1condensationB-酮脂酰-ACP合酶CO2OSCHCCH2C0HSMTKS0O1β-酮脂酰-ACP合酶ACPKRCH3-CS-合酶+HOOC-CH,-C~SACPAT0OHDERuCH3-C-CH,-C~SACP+合酶-SH+CO2β-Ketobutyryl-ACP
(3)缩合反应 KS : β-酮脂酰-ACP合酶
(4)还原反应OCH2CSCH3-COKR:HSB-酮脂酰-ACP还原酶MTKS堂ACPKRATCH3-CHCH2-CSHDEROHHSβ-Ketobutyryl-ACPKSMTACPNADPH +H+KRAT②NADP+HDERreduction ofβ-ketogroupβ-Hydroxybutyryl-ACPO=Oβ-酮脂酰-ACP还原酶CH3-C-CH2-C~SACP +NADPH++H+OH9CH,-CH-CH,-C~SACP +NADP+D-β-羟丁酰-ACP
(4)还原反应 KR: β-酮脂酰-ACP还原酶
0(5)脱水反应CH3CHCHC-SHSHD:B-羟脂酰-ACP脱水酶MTKS0ACPKRATSCH3CH-CH2-0ERHDOHHStrans-2-Butenoyl-ACPKSMTACPKRATH20HDERdehydrationβ-Hydroxybutyryl-ACPOH1CH, Hβ-羟脂酰-ACP脱水酶1C-C+H,0CH-CH-CH,-C～SACP132HC~SACP10
(5)脱水反应 HD: β-羟脂酰-ACP脱水酶
0(6)再还原反应CSCHSCH2CH,HSKSMTACPKRATERHDButyryl-ACPER:NADP+B-烯脂酰-ACP还原酶Oreduction ofNADPH+H+doublebond0CH3CHCH-CSHSMTKSCH, H-烯脂酰-ACP还原酶1cc+NADPH+H+ACPKRAT0/HC~SACPERHD11CH-CH,-CH-C~SACP+NADP+0（丁酰-ACP)trans-A2-Butenoyl-ACP
(6)再还原反应 ER: β-烯脂酰-ACP还原酶