scholarly journals Overproduction of a Functional Fatty Acid Biosynthetic Enzyme Blocks Fatty Acid Synthesis inEscherichia coli

1998 ◽  
Vol 180 (17) ◽  
pp. 4596-4602 ◽  
Author(s):  
Satyanarayana Subrahmanyam ◽  
John E. Cronan
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Acyl Carrier Protein ◽  
State Level ◽  
Acid Synthesis ◽  
The Other ◽  
Carrier Protein ◽  
Biosynthetic Enzyme ◽  
E Coli ◽  
Malonyl Coa

ABSTRACT β-Ketoacyl-acyl carrier protein (ACP) synthetase II (KAS II) is one of three Escherichia coli isozymes that catalyze the elongation of growing fatty acid chains by condensation of acyl-ACP with malonyl-ACP. Overexpression of this enzyme has been found to be extremely toxic to E. coli, much more so than overproduction of either of the other KAS isozymes, KAS I or KAS III. The immediate effect of KAS II overproduction is the cessation of phospholipid synthesis, and this inhibition is specifically due to the blockage of fatty acid synthesis. To determine the cause of this inhibition, we examined the intracellular pools of ACP, coenzyme A (CoA), and their acyl thioesters. Although no significant changes were detected in the acyl-ACP pools, the CoA pools were dramatically altered by KAS II overproduction. Malonyl-CoA increased to about 40% of the total cellular CoA pool upon KAS II overproduction from a steady-state level of around 0.5% in the absence of KAS II overproduction. This finding indicated that the conversion of malonyl-CoA to fatty acids had been blocked and could be explained if either the conversion of malonyl-CoA to malonyl-ACP and/or the elongation reactions of fatty acid synthesis had been blocked. Overproduction of malonyl-CoA:ACP transacylase, the enzyme catalyzing the conversion of malonyl-CoA to malonyl-ACP, partially relieved the toxicity of KAS II overproduction, consistent with a model in which high levels of KAS II blocks access of the other KAS isozymes to malonyl-CoA:ACP transacylase.

scholarly journals Structure of the mitochondrial β-ketoacyl-[acyl carrier protein] synthase fromArabidopsisand its role in fatty acid synthesis

FEBS Letters ◽  
2004 ◽  
Vol 577 (1-2) ◽  
pp. 170-174 ◽  
Author(s):  
Johan G. Olsen ◽  
Anne V. Rasmussen ◽  
Penny von Wettstein-Knowles ◽  
Anette Henriksen
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Acyl Carrier Protein ◽  
Acid Synthesis ◽  
Carrier Protein

scholarly journals Stromal concentrations of coenzyme A and its esters are insufficient to account for rates of chloroplast fatty acid synthesis: evidence for substrate channelling within the chloroplast fatty acid synthase

1997 ◽  
Vol 327 (1) ◽  
pp. 267-273 ◽  
Author(s):  
P. Grattan ROUGHAN
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Fatty Acid Synthase ◽  
Acyl Carrier Protein ◽  
Acid Synthesis ◽  
Acetyl Coa ◽  
Minimal Processing ◽  
Malonyl Coa ◽  
Substrate Channelling ◽  
Isolated Chloroplasts

Concentrations of total CoAs in chloroplasts freshly isolated from spinach and peas were 10–20 μM, assuming a stromal volume of 66 μl per mg of chlorophyll. Acetyl-CoA and CoASH constituted at least 90% of the total CoA in freshly isolated chloroplasts. For a given chloroplast preparation, the concentration of endogenous acetyl-CoA was the same when extractions were performed using HClO4, trichloroacetic acid, propan-2-ol or chloroform/methanol, and the extracts analysed by quantitative HPLC after minimal processing. During fatty acid synthesis from acetate, concentrations of CoASH within spinach and pea chloroplasts varied from less than 0.1 to 5.0 μM. Malonyl-CoA concentrations were also very low (< 0.1–3.0 μM) during fatty acid synthesis but could be calculated from radioactivity incorporated from [1-14C]acetate. Concentrations of CoASH in chloroplasts synthesizing fatty acids could be doubled in the presence of Triton X-100, suggesting that the detergent stimulates fatty acid synthesis by increasing the turnover rate of acyl-CoA. However, although taken up, exogenous CoASH (1 μM) did not stimulate fatty acid synthesis by permeabilized spinach chloroplasts. Calculated rates for acetyl-CoA synthetase, acetyl-CoA carboxylase and malonyl-CoA–acyl-carrier-protein transacylase reactions at the concentrations of metabolites measured here are < 0.1–4% of the observed rates of fatty acid synthesis from acetate by isolated chloroplasts. The results suggest that CoA and its esters are probably confined within, and channelled through, the initial stages of a fatty acid synthase multienzyme complex.

scholarly journals Purification and Biochemical Characterization of theMycobacterium tuberculosisβ-Ketoacyl-acyl Carrier Protein Synthases KasA and KasB

2001 ◽  
Vol 276 (50) ◽  
pp. 47029-47037 ◽  
Author(s):  
Merrill L. Schaeffer ◽  
Gautam Agnihotri ◽  
Craig Volker ◽  
Howard Kallender ◽  
Patrick J. Brennan ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Acyl Carrier Protein ◽  
Acid Synthesis ◽  
Mycolic Acid ◽  
Carrier Protein ◽  
Mycolic Acids ◽  
E Coli ◽  
Long Chain

Mycolic acids are vital components of theMycobacterium tuberculosiscell wall, and enzymes involved in their formation represent attractive targets for the discovery of novel anti-tuberculosis agents. Biosynthesis of the fatty acyl chains of mycolic acids involves two fatty acid synthetic systems, the multifunctional polypeptide fatty acid synthase I (FASI), which performsde novofatty acid synthesis, and the dissociated FASII system, which consists of monofunctional enzymes, and acyl carrier protein (ACP) and elongates FASI products to long chain mycolic acid precursors. In this study, we present the initial characterization of purified KasA and KasB, two β-ketoacyl-ACP synthase (KAS) enzymes of theM. tuberculosisFASII system. KasA and KasB were expressed inE. coliand purified by affinity chromatography. Both enzymes showed activity typical of bacterial KASs, condensing an acyl-ACP with malonyl-ACP. Consistent with the proposed role of FASII in mycolic acid synthesis, analysis of various acyl-ACP substrates indicated KasA and KasB had higher specificity for long chain acyl-ACPs containing at least 16 carbons. Activity of KasA and KasB increased with use ofM. tuberculosisAcpM, suggesting that structural differences between AcpM andE. coliACP may affect their recognition by the enzymes. Both enzymes were sensitive to KAS inhibitors cerulenin and thiolactomycin. These results represent important steps in characterizing KasA and KasB as targets for antimycobacterial drug discovery.

scholarly journals NovelXanthomonas campestrisLong-Chain-Specific 3-Oxoacyl-Acyl Carrier Protein Reductase Involved in Diffusible Signal Factor Synthesis

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Zhe Hu ◽  
Huijuan Dong ◽  
Jin-Cheng Ma ◽  
Yonghong Yu ◽  
Kai-Hui Li ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Xanthomonas Campestris ◽  
Octanoic Acid ◽  
Acyl Carrier Protein ◽  
Acid Synthesis ◽  
Carrier Protein ◽  
Content Type ◽  
Diffusible Signal Factor ◽  
Acyl Chains

ABSTRACTThe precursors of the diffusible signal factor (DSF) family signals ofXanthomonas campestrispv.campestrisare 3-hydroxyacyl-acyl carrier protein (3-hydroxyacyl-ACP) thioesters having acyl chains of 12 to 13 carbon atoms produced by the fatty acid biosynthetic pathway. We report a novel 3-oxoacyl-ACP reductase encoded by theX. campestrispv.campestrisXCC0416 gene (fabG2), which is unable to participate in the initial steps of fatty acyl synthesis. This was shown by the failure of FabG2 expression to allow growth at the nonpermissive temperature of anEscherichia colifabGtemperature-sensitive strain. However, when transformed into theE. colistrain together with a plasmid bearing theVibrio harveyiacyl-ACP synthetase gene (aasS), growth proceeded, but only when the medium contained octanoic acid.In vitroassays showed that FabG2 catalyzes the reduction of long-chain (≥C8) 3-oxoacyl-ACPs to 3-hydroxyacyl-ACPs but is only weakly active with shorter-chain (C4, C6) substrates. FabG1, the housekeeping 3-oxoacyl-ACP reductase encoded within the fatty acid synthesis gene cluster, could be deleted in a strain that overexpressedfabG2but only in octanoic acid-supplemented media. Growth of theX. campestrispv.campestrisΔfabG1strain overexpressingfabG2requiredfabHfor growth with octanoic acid, indicating that octanoyl coenzyme A is elongated byX. campestrispv.campestrisfabH. Deletion offabG2reduced DSF family signal production, whereas overproduction of either FabG1 or FabG2 in the ΔfabG2strain restored DSF family signal levels.IMPORTANCEQuorum sensing mediated by DSF signaling molecules regulates pathogenesis in several different phytopathogenic bacteria, includingXanthomonas campestrispv.campestris. DSF signaling also plays a key role in infection by the human pathogenBurkholderia cepacia. The acyl chains of the DSF molecules are diverted and remodeled from a key intermediate of the fatty acid synthesis pathway. We report aXanthomonas campestrispv.campestrisfatty acid synthesis enzyme, FabG2, of novel specificity that seems tailored to provide DSF signaling molecule precursors.

scholarly journals The Two Functional Enoyl-Acyl Carrier Protein Reductases of Enterococcus faecalis Do Not Mediate Triclosan Resistance

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
Lei Zhu ◽  
Hongkai Bi ◽  
Jincheng Ma ◽  
Zhe Hu ◽  
Wenbin Zhang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Enterococcus Faecalis ◽  
Fatty Acid Synthesis ◽  
Acyl Carrier Protein ◽  
Acid Synthesis ◽  
Carrier Protein ◽  
Content Type ◽  
Enoyl Acp Reductase ◽  
Triclosan Resistance

ABSTRACTEnoyl-acyl carrier protein (enoyl-ACP) reductase catalyzes the last step of the elongation cycle in the synthesis of bacterial fatty acids. TheEnterococcus faecalisgenome contains two genes annotated as enoyl-ACP reductases, a FabI-type enoyl-ACP reductase and a FabK-type enoyl-ACP reductase. We report that expression of either of the two proteins restores growth of anEscherichia colifabItemperature-sensitive mutant strain under nonpermissive conditions.In vitroassays demonstrated that both proteins support fatty acid synthesis and are active with substrates of all fatty acid chain lengths. Although expression ofE. faecalis fabKconfers toE. colihigh levels of resistance to the antimicrobial triclosan, deletion offabKfrom theE. faecalisgenome showed that FabK does not play a detectable role in the inherent triclosan resistance ofE. faecalis. Indeed, FabK seems to play only a minor role in modulating fatty acid composition. Strains carrying a deletion offabKgrow normally without fatty acid supplementation, whereasfabIdeletion mutants make only traces of fatty acids and are unsaturated fatty acid auxotrophs.IMPORTANCEThe finding that exogenous fatty acids support growth ofE. faecalisstrains defective in fatty acid synthesis indicates that inhibitors of fatty acid synthesis are ineffective in counteringE. faecalisinfections because host serum fatty acids support growth of the bacterium.

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