Acetyl-S-ACP

H2O -H CH3CH = CHCO-S-ACP acetyl S-ACP + HS-E - acetyl-S-E -h ACP-SH acetyl-S-E -H malonyl-S-ACP... 

A similar long arm is apparent in biotin (7.9), again enzyme bound through a lysine residue. The coenzyme (7.9) assists in the carboxylation of acetyl-CoA 1.8) with carbon dioxide yielding malonyl-CoA 1.14). Exchange of both acetyl-CoA and malonyl-CoA occurs with acyl carrier proteins (AGP) having free thiol groupings. Condensation then occurs between acetyl-S-ACP and malonyl-S-ACP with simultaneous decarboxylation the carboxylate anion is transferred into the new bond (Scheme 1.2) [6]. Subsequent steps involve reduction, dehydration and double-bond saturation. They... 

The biosynthesis of fatty acids is accomplished two carbons at a time by an enzyme complex called fatty acid synthetase. The biochemical reactions involved in fatty acid synthesis are described in Special Topic E WileyPLUS). Each of these biochemical reactions has a counterpart in synthetic reactions you have studied. Consider the biochemical reactions involved in adding each —CH2CH2— segment during fatty acid biosynthesis (those in Special Topic E that begin with acetyl-S-ACP and malonyl-S-ACP, and end with butyryl-S-ACP). Write laboratory synthetic reactions using reagents and conditions you have studied (not biosynthetic reactions) that would accomplish the same sequence of transformations (i.e., the condensation-decarboxylation, ketone reduction, dehydration, and alkene reduction steps). 

Ql. Acetyl-S-ACP to malonyl-S-ACP to stearic acid, desaturated to oleic acid, chain extended by three acetate units to a C24 unsaturated acid, and decarboxylation gives (Z)-9-tricosene. 

Is a specific Inhibitor of type II fatty acid synthetase In higher plants and . coll 12401. The acetyl-CoA ACP S-acety1-transferase Is the apparent specific site of Inhibition 12411. Another antibiotic, cerulenin (structure not shown) Inhbits -ketococy1-ACP synthetase I In bacteria, fungi, and plants, but also Is Inhibitory to other sites such as polyketide and sterol biosynthesis 1242-2441. Cerulenin and thiolactomycin Inhibited CQ14W-acetate Incorporation Into fatty acids at 150 values of 50 and 4 uM, respectively 12451. Recently cydohexanedlone herbicides have been shown to Inhibit lipid biosynthesis by Inhibition of acetyl-CoA carboxylase 12461. 

The first reaction, catalyzed by Acetyl-CoA ACP transacylase, transfers an acetyl group from Coenzyme A to the cysteinyl-S on ACPi. 

Spatially, the enzyme activities are arranged into three different domains. Domain 1 catalyzes the entry of the substrates acetyl CoA and malonyl CoA by [ACPj-S-acetyltransferase [1] and [ACPJ-Smalonyl transferase [2] and subsequent condensation of the two partners by 3-oxoacyl-[ACP] synthase [3]. Domain 2 catalyzes the conversion of the 3-0X0 group to a CH2 group by 3-oxoacyl-[ACP]-reductase [4], 3-hydroxyacyl-[ACP -dehydratase [5], and enoyl-[ACP]-re-... 

The results reveal that baker s yeast is a potent source for precursors of 2-acetyl-l-pyrroline. It appears likely that the flavor compound is formed in the yeast cells from proline and dihydroxyacetone phosphate via 1-pyrroline and pyruvaldehyde. This is corroborated by the results of c-labeling experiments which showed that the acetyl group in the Acp stems from a sugar degradation product and that the pyrroline ring was derived from proline. 

Claisen-like condensation of malonyl ACP with acetyl synthase occurs, followed by decarboxylation to yield acetoacetyl ACP, a /S-keto thioester. 

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