Self-acylation properties of type II fatty acid biosynthesis acyl carrier protein

Acyl carrier protein (ACIP) plays a central role in many metabolic processes inside the cell, and almost 4% of the total enzymes inside the cell require it as a cofactor. Here, we report self-acylation properties in ACPs from Plasmodium falciparum and Brassica napus that are essential components of type II fatty acid biosynthesis (FAS II), disproving the existing notion that this phenomenon is restricted only to ACPs involved in polyketide biosynthesis. We also provide strong evidence to suggest that catalytic self-acylation is intrinsic to the individual ACP. Mutational analysis of these ACPs revealed the key residue(s) involved in this phenomenon. We also demonstrate that these FAS 11 ACPs exhibit a high degree of selectivity for self-acylation employing only dicarboxylic acids as substrates. A plausible mechanism for the self-acylation reaction is also proposed.

Rationalizing the effects of amino acid side chain, pyridine, and imidazole on the assembly and reversible disassembly of a octanuclear Cu(III) complex

This paper reports the observation of a reversible disassembly process for a previously reported octanuclear Cu(II) complex with imidazole. To identify the factors responsible for the process, five Cu(II) complexes of different nuclearity with different amino acid-derived tetradentate ligands were structurally characterized. The results show that the coordination geometry preference of Cu(II), the tendency of imidazole to act as in-plane ligand, and H-bonding played important role in the formation and disassembly of the octanuclear complex. A general scheme describing the effect of different amino acid side arms, solvents, and exogenous ligands on the nuclearity of the Cu(II) complexes has been presented. The crystals of the complexes also showed formation of multifaceted networks in the resulting complexes.

Synthesis, Characterization and Evaluation of Cytotoxicity of New Aminophosphonic Acid Diesters in Human Leukemia Cells

A series of novel fluoroaminophosphates 4a-4j were synthesized by one-pot method in presence of tetramethylguanidine (TMG) as a catalyst and were characterized by elemental analysis, FTIR, H-1, C-13, P-31, F-19 NMR, and mass spectra. All the title compounds were evaluated forin vitro cytotoxicity against leukemic cell line derived from T-cells of leukemia patient (CEM cells) by Trypan blue exclusion and MTT assays, and these were found to exert concentration dependent cytotoxic effects. Among them 4f, 4g & 4j possessed marked cytotoxicity. 4g (with IC50 value of 6 mu M) had emerged as lead compound.

An expeditious enantiospecific total synthesis of (+)-7-epi-goniofufurone

Stereoselective synthesis of styryl lactone, (+)-7-epi-goniofufurone was achieved in high yield via simple transformations from tartaric acid. The key step involves the successive stereoselective reduction of ketones with borohydride and selectride.

Stereoselective Synthesis of C1-C18 Region of Palmerolide A from Tartaric Acid

A stereoselective synthesis of the C1-C18 region of marine natural product palmerolide A from chiral pool tartaric acid is presented. The key synthetic sequence includes the elaboration of a gamma-oxo-amide derived from tartaric acid and alkene formation involving Boord type fragmentation.

Modular design of synthetic protein mimics. Crystal structure of two seven-residue helical peptide segments linked by .epsilon.-aminocaproic acid

Two seven-residue helical segments, Val-Ala-Leu-Aib-Val-Ala-Leu, were linked synthetically with an epsilon-aminocaproic acid (Acp) linker with the intention of making a stable antiparallel helix-helix motif. The crystal structure of the linked peptide Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-Acp-Val-Ala-Leu-Aib-Val-Ala-Leu-OMe (1) shows the two helices displaced laterally from each other by the linker, but the linker has not folded the molecule into a close-packed antiparallel conformation. Two strong intermolecular NH...O = C hydrogen bonds are formed between the top of the lower helix of one molecule and the bottom of the upper helix in a laterally adjacent molecule to give the appearance of an extended single helix. The composite peptide with Boc and OMe end groups, C76H137N15O18.H2O, crystallize in space group P2(1) with a = 8.802 (1) angstrom, b = 20.409 (4) angstrom, c = 26.315 (3) angstrom, and beta = 90.72 (1)degrees; overall agreement R = 7.86% for 5030 observed reflections (\F(o)\ > 3-sigma(F)); resolution = 0.93 angstrom. Limited evidence for a more compact conformation in solution consistent with an antiparallel helix arrangement is obtained by comparison of the HPLC retention times and CD spectra of peptide 1 with well-characterized continuous helices of similar length and sequence.

A combined extended and helical backbone for Boc-(Ala-Leu-Ac(7)c-)(2)-OMe

The structure of the peptide Boc-Ala-Leu-Ac(7)c-Ala-Leu-Ac(7)c-OMe (Ac(7)c,1-aminocycloheptane-1-carboxylic acid) is described in crystals. The presence of two Ac(7)c residues was expected to stabilize a 3(10)-helical fold. Contrary to expectation the structural analysis revealed an unfolded amino terminus, with Ala(1) adopting an extended beta-conformation (phi = -93degrees,psi = 112degrees). Residues 2-5 form a 3(10)-helix, stabilized by three successive intramolecular hydrogen bonds. Notably, two NH groups Ala(1) and Ac(7)c(3) do not form any hydrogen bonds in the crystal. Peptide assembly appears to be dominated by packing of the cycloheptane rings that stack against one another within the molecule and also throughout the crystal in columns.

Mass Spectrometry-Based Systems Approach for Identification of Inhibitors of Plasmodium falciparum Fatty Acid Synthase{triangledown}

The emergence of strains of Plasmodium falciparum resistant to the commonly used antimalarials warrants the development of new antimalarial agents. The discovery of type II fatty acid synthase (FAS) in Plasmodium distinct from the FAS in its human host (type I FAS) opened up new avenues for the development of novel antimalarials. The process of fatty acid synthesis takes place by iterative elongation of butyryl-acyl carrier protein (butyryl-ACP) by two carbon units, with the successive action of four enzymes constituting the elongation module of FAS until the desired acyl length is obtained. The study of the fatty acid synthesis machinery of the parasite inside the red blood cell culture has always been a challenging task. Here, we report the in vitro reconstitution of the elongation module of the FAS of malaria parasite involving all four enzymes, FabB/F (β-ketoacyl-ACP synthase), FabG (β-ketoacyl-ACP reductase), FabZ (β-ketoacyl-ACP dehydratase), and FabI (enoyl-ACP reductase), and its analysis by matrix-assisted laser desorption-time of flight mass spectrometry (MALDI-TOF MS). That this in vitro systems approach completely mimics the in vivo machinery is confirmed by the distribution of acyl products. Using known inhibitors of the enzymes of the elongation module, cerulenin, triclosan, NAS-21/91, and (–)-catechin gallate, we demonstrate that accumulation of intermediates resulting from the inhibition of any of the enzymes can be unambiguously followed by MALDI-TOF MS. Thus, this work not only offers a powerful tool for easier and faster throughput screening of inhibitors but also allows for the study of the biochemical properties of the FAS pathway of the malaria parasite.

Mass Spectrometry-Based Systems Approach for Identification of Inhibitors of Plasmodium falciparum Fatty Acid Synthase{triangledown}

The emergence of strains of Plasmodium falciparum resistant to the commonly used antimalarials warrants the development of new antimalarial agents. The discovery of type II fatty acid synthase (FAS) in Plasmodium distinct from the FAS in its human host (type I FAS) opened up new avenues for the development of novel antimalarials. The process of fatty acid synthesis takes place by iterative elongation of butyryl-acyl carrier protein (butyryl-ACP) by two carbon units, with the successive action of four enzymes constituting the elongation module of FAS until the desired acyl length is obtained. The study of the fatty acid synthesis machinery of the parasite inside the red blood cell culture has always been a challenging task. Here, we report the in vitro reconstitution of the elongation module of the FAS of malaria parasite involving all four enzymes, FabB/F (β-ketoacyl-ACP synthase), FabG (β-ketoacyl-ACP reductase), FabZ (β-ketoacyl-ACP dehydratase), and FabI (enoyl-ACP reductase), and its analysis by matrix-assisted laser desorption-time of flight mass spectrometry (MALDI-TOF MS). That this in vitro systems approach completely mimics the in vivo machinery is confirmed by the distribution of acyl products. Using known inhibitors of the enzymes of the elongation module, cerulenin, triclosan, NAS-21/91, and (–)-catechin gallate, we demonstrate that accumulation of intermediates resulting from the inhibition of any of the enzymes can be unambiguously followed by MALDI-TOF MS. Thus, this work not only offers a powerful tool for easier and faster throughput screening of inhibitors but also allows for the study of the biochemical properties of the FAS pathway of the malaria parasite.

Catalytic cracking of acetic acid to acetic anhydride

Catalytic cracking of acetic acid using triethyl phosphate and silica gel catalysts was investigated. The desired reaction leading to ketene is accompanied by side reactions: two parallel with respect to acetic acid decomposition and the consecutive ketene decomposition reactions. Effect of temperature, catalyst concentration, space velocity, and pressure was studied in detail. Triethyl phosphate was found to be a much better catalyst than silica gel. The optimum yield of ketene was obtained at 750° C, 100 mm. of Hg pressure, and apparent contact time of 5.687 × 10-4 hour.

Synthetic application of the diels-alder adduct of β-trans-ocimene and maleic anhydride-II. An approach towards the synthesis of valerenic acid

By a series of reactions the Diels-Alder adduct IV of maleic anhydride and β-trans-Ocimene gave 1-hydroxy-1,4-dimethyl-7-hydroxymethyloctahydroindane (XII). Its further synthetic elaboration furnished 1,4-dimethyl-7-(2-ethoxycarbonyl-1-propenyl)-Δ1-octahydroindane of the valerenic acid skeleton.

Studies in the polarography of metal-amino acid complexes -Part II. Lead

1. The polarographic behaviour of glycine, α-alanine, β-alanine, valine, aspartic acid, glutamic acid and asparagine complexes of lead has been studied at various pH values and in presence of (1) NaOH, (2) Na2CO3 and (3) NH4 NO3+NH4OH. All the polarographic waves have been found to be reversible. 2. Experiments conducted on the effect of variation of pH, i.e., 7acid have indicated the formation of Pb A and Pb A2. The data have been analysed employing the equations developed by DeFord and Hume as modified by McKenzie and Mellor. 3. Only pure complexes are produced below pH 11·2 in the case of aspartic acid, glutamic acid and glycine, while mono hydroxy complexes are produced in α-alanine, valine and asparagine systems. 4. It has been found that no mixed hydroxy and mixed ammonia complexes are produced in presence of sodium hydroxide and ammonia-ammonium nitrate, respectively. However evidence is obtained for the formation of mixed carbonate complexes in glycine and aspartic acid systems in presence of sodium carbonate. 5. Thermodynamic data have been calculated from polarographic measurements for 18 complexes. 6. The suitability of incorporating amino acids in base solutions for the polarographic estimation of lead has been tested.

Studies in sesquiterpenes-XIX. Action of perbenzoic acid on longifolene

Oxidation of longifolene, a mono-olefinic sesquiterpene, with a chloroform solution of perbenzoic acid proceeded to almost two mole consumption of the peracid to furnish a number of products, important ones being an α-ketol, a norketone (longicamphenilone) and the corresponding C14-alcohols. Under certain conditions it has been possible to arrest the reaction at one mole consumption and to isolate longifolene-α-epoxide, which is the major product; some amounts of epimeric longifolaldehydes and longicamphenilone were also formed. Further action of perbenzoic acid on longifolene oxide and longifolaldehydes has been investigated and the results used to interpret the mechanism of abnormal peracid oxidation of longifolene.

Biosynthesis of β-N-oxalyl-l-α,β-diaminopropionic acid, the lathyrus sativus neurotoxin

The biosynthesis of β-N-oxalyl-l-α,β-diaminopropionic acid (ODAP) the Lathyrus sativus neurotoxin has been found to follow the scheme depicted below: {A figure is presented}. The first reaction is catalysed by oxalyl-CoA synthetase which has properties similar to that of the enzyme in peas. The second reaction is catalysed by another enzyme which is specific to L. sativus and is designated as oxalyl-CoA-α,β-diaminopropionic acid oxalyl transferase. The enzymes have been purified by about 60-fold and their properties studied. A partial resolution of the two enzyme activities has been achieved using CM-sephadex columns.

Stimulation by thyrotropin, long-acting thyroid stimulator, and dibutyryl 3′, 5′-adenosine monophosphate of protein and ribonucleic acid synthesis and ribonucleic acid polymerase activities in porcine thyroid in Vitro

The in vitro incorporation of [3H]uridine into RNA and [3H]leucine into protein in slices of porcine thyroid was studied. Thyrotropin (10-500 mU/ml of medium), when added with [3H]uridine, inhibited incorporation into RNA, but as little as 10 mU of thyrotropin per ml stimulated incorporation of [3H]orotic acid into RNA. Uridine kinase (EC 2.7.1.48) was found to be inhibited in slices incubated with thyrotropin whereas UMP 5′ nucleotidase (EC 2.1.3.5) was not. Preincubation of slices with thyrotropin (5-50 mU/ml) led to enhanced incorporation of subsequently added [3H]uridine and [3H]leucine. When slices were preincubated with long-acting thyroid stimulator-IgG (2.5 or 5 mg per ml of medium) incorporation of [3H]uridine and [3H]leucine was similarly enhanced, with the smaller concentration being more effective. Without preincubation these stimulatory effects were mimicked by 1 mM dibutyryl 3′,5′-AMP and, to a lesser extent, 1 mM 3′,5′-AMP. AMP and ATP also stimulated [3H]uridine incorporation in this system but only after more prolonged periods of incubation than were required for the other nucleotides. RNA polymerase (EC 2.7.7.6) activity measured in isolated thyroid nuclei had two components, one Mg2+-stimulated and the other requ ring Mn2+ and high salt content [0.4 M (NH4)2SO4]. These activities, and particularly the former, were enhanced if thyroid slices were incubated with thyrotropin (5-100 mU/ml of medium), 2.5 mg or 5.0 mg of long-acting thyroid stimulator-IgG per ml, or 1 mM dibutyryl 3′,5′-AMP, before isolatior of the nuclei and measurement of enzyme activities; 1 mM AMP, ADP, or 2′,3′-GMP had no influence. Added directly to the nuclei, thyrotropin, long-acting thyroid stimulator-IgG, and dibutyryl 3′,5′-AMP had no effect on RNA polymerase activities. These data are seen as affording evidence for mediation by 3′,5′-AMP of effects of thyrotropin and long-acting thyroid stimulator on thyroid RNA and protein synthesis, at least in part through an indirect stimulation of nuclear RNA polymerase activities.