ACP-acetyltransferase

J AcetyUCoA carboxylase. Incorporation of metabolically derived acetyl-CoA into fatty acid synthesis is believed generally to involve three major enzyme systems, namely acetyl-CoA carboxylase (EC 6.4.1.2), [acyl-carrier protein] (ACP) acetyltransferase (EC 2.3.1.38)... 

The apparent ready reversibility of the reactions catalyzed by [ACP] acetyltransferase and [ACP] malonyltransferase is not suggestive that these enzymes are appropriate candidates for consideration as major regulatory enzyme systems (Walsh et al., 1990 Post-Beittenmiller et al., 1991). This conclusion is supported by the finding that [ACP] acetyltransferase showed very low specific activity in developing seeds of Cuphea lutea, rape and safflower (Shimakata and Stumpf, 1983). None the less under in vitro conditions, increased levels of [ACP] acetyltransferase enhances the synthesis of medium-chain fatty acids (Stumpf, 1989). This observation may only serve to emphasize the definite involvement of this enzyme system in fatty acid synthesis without implying that it is under major regulation. 

As shown in Table 1, of individual six enzymes from E. coli ACP acetyltransferase and 3-ketoacyl-ACP synthase were inhibited more than 50 % at 3-5 pM TLM, although the other enzymes retained full activities at this concentration. TLM reversibly inhibited fatty acid synthase. The inhibition of acetyltransferase was competitive for ACP, but uncompetitive for acetyl-CoA. The inhibition of 3-ketoacyl-ACP synthase was also competitive for malonyl-ACP but noncompetitive for acetyl-ACP (Fig. 1). 

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