④还原 CHs-C-CH2-( HS D-邛羟丁酰ACP KS MT AT ACP R CH3一CH-CH2-C-S ER HD OH HS 8-Ketobutyryl-ACP KS MT NADPH +H+ AT ACP KR NADP+ reduction of ER HD 8-keto group B酮酰ACP还原酶，KR B-Hydroxybutyryl-ACP ④还原 β 酮酰ACP还原酶，KR D-αβ 羟丁酰ACP