Pyrolysis of β-Hydroxy Amino Acids,Especially l-Serine

From the pyrolysis of l-serine, ten volatile compounds including several pyrazines were identified. Pyrazines were also found from the pyrolysis of l-threonine, but not from that of alanine and considered to be characteristic pyrolysis products of β-hydroxy amino acids. At the same time, diketopiperazines, amines and carbonyl compounds were also found in addition to those described above. Formation mechanism of pyrazine compounds was also discussed.     

Effects of 20 Standard Amino Acids on the Growth,Total Fatty Acids Production,and γ-Linolenic Acid Yield in Mucor circinelloides

Twenty standard amino acids were examined as single nitrogen source on the growth, total fatty acids production, and yield of γ-linolenic acid (GLA) in Mucor circinelloides. Of the amino acids, tyrosine gave the highest biomass and lipid accumulation and thus resulted in a high GLA yield with respective values of 17.8 g/L, 23 % (w/w, dry cell weight, DCW), and 0.81 g/L, which were 36, 25, and 72 % higher than when the fungus was grown with ammonium tartrate. To find out the potential mechanism underlying the increased lipid accumulation of M. circinelloides when grown on tyrosine, the activity of lipogenic enzymes of the fungus during lipid accumulation phase was measured. The enzyme activities of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and ATP-citrate lyase were up-regulated, while NADP-isocitrate dehydrogenase was down-regulated by tyrosine during the lipid accumulation phase of the fungus which suggested that these enzymes may be involved in the increased lipid biosynthesis by tyrosine in this fungus.     

β-Phenylmercapto-cis- and trans-cinnamic Acids

β-(p-Chlorophenyl) mercaptocinnamic acid and β-(p-acetamidophenyl) mercaptocinnamic acid were synthesized and separated into cis- and trans-isomers of each. Their configurations were determined by ring closure to be thioflavons under mild conditions. trans-Acids have an absorption band at 8.3μ while cis-acids do not have such band. Other physical methods generally used to determine the geometrical configuration were of no avail for these compounds carrying a bulky group at β-position. cis-Acid was produced via isomerization from the trans-ester during the procedure of saponification.     

Nucleic Acids and Signal Transduction International Symposium,July 26–29, 2000; Waltham,MA, United States

Russian Journal of Bioorganic Chemistry -     

The Synthesis of α-Methylamino Acids

α-Methyltryptophan, α-methylhistidine, and α-methyldopa were prepared by the reaction of α-isocyanopropionates with gramine methiodide, the acetoxymethylimidazole derivative, and protected 3,4-dihydroxybenzyl bromides, respectively.     

Is the Profile of Fatty Acids,Tocopherols, and Amino Acids Suitable to Differentiate Pinus armandii Suspicious to Be Responsible for the Pine Nut Syndrome from Other Pinus Species?

Pinus armandii is suspicious to be responsible for the Pine Nut Syndrome, a long lasting bitter and metallic taste after the consumption of pine nuts. To find chemical characteristic features for the differentiation of P. armandii from other Pinus species, 41 seed samples of the genus Pinus from 22 plant species were investigated regarding the content and the composition of fatty acids, tocopherols, and amino acids. The predominant fatty acids in the seed oils were linoleic acid (35.2 – 58.2 g/100 g), oleic acid (14.6 – 48.5 g/100 g), and pinolenic acid (0.2 – 22.4 g/100 g), while the vitamin‐E‐active compounds were dominated by γ‐tocopherol. The amino acid composition was mainly characterized by arginine and glutamic acid with amounts between 0.9 and 8.9 g/100 g as well as 2.1 g/100 g and 8.3 g/100 mg. On the basis of this investigation, a Principle Component Analysis has been used to identify the most important components for the differentiation of P. armandii from other Pinus species. Using the data for glutamic acid, 20:2Δ^5,11, 18:3Δ^5,9,12, 18:1Δ⁹, and oil content, a classification of the 41 samples into four different groups by cluster analysis was possible, but the characteristic features of P. armandii were too close to some other members of the genus Pinus, making a clear differentiation of this species difficult. Nevertheless, the investigation showed the similarities of different members of the genus Pinus with regard to fatty acids, vitamin‐E‐active compounds, and amino acids.     

Studies on α-Alkyl-α-amino Acids

Effects of cytokinins were studied on rotenone-sensitive NADH dehydrogenase in mitochondria from fresh potato tubers (Solarium tuberosum), in consideration of the operation of external and rotenone-insensitive internal NADH dehydrogenases that has not been fully accounted for in previous studies. In submitochondrial particles (smp), zeatin was only weakly active, and zeatin riboside (ZR) was inactive. Inhibition rates at 400 μM of isopentenyladenine (iP) and isopentenyladenosine (iPA) were 45% and 30%, respectively, and that of BA (BA) was 64%. In intact mitochondria, the inhibition by iP and BA significantly increased, I₅₀ being 50 and 250 μM, respectively, but that by zeatin and iPA decreased. A structure–activity study showed that hydrophobic and steric factors are important for the activity. Cytokinins inhibited the electron flow via natural quinone more strongly than that via synthetic quinone. These results suggest that among the cytokinins the species that can regulate the electron transport is iP rather than its riboside or zeatin.     

Octapeptide Analogs of Somatostatin Containing α,α-Dialkylated Amino Acids with Potent Anticancer Activity

We describe the synthesis and anticancer activities of octapeptide analogs of somatostatin incorporating α,α-dialkylated amino acids. The designed analogs of somatostatin are: d-Phe¹-Cys²-Tyr³-d-Trp⁴-Orn⁵-Xxx⁶-Pen⁷-Thr⁸-NH₂ where Xxx=α-Aminoisobutyric acid (Aib), Diethyl glycine (Deg), 1-Aminocyclopentane carboxylic acid (Ac5c), and, d-Phe¹-Cys²-Tyr³-d-Trp⁴-Lys⁵-Ac5c⁶-Pen⁷-Thr⁸-NH₂ (disulphide bond between Cys² and Pen⁷ in all analogs). The conformational studies two of the designed analogs were carried out by NMR techniques and the experimental results suggest a β-turn structure for one of the designed analog. In vivo tumor regression study of two designed analogs on human primary colon tumor xenografts in nude mice demonstrates the anticancer potential of the synthesized analogs.     

How Do Haloarchaea Synthesize Aromatic Amino Acids?

Genomic analysis of H. salinarum indicated that the de novo pathway for aromatic amino acid (AroAA) biosynthesis does not follow the classical pathway but begins from non-classical precursors, as is the case for M. jannaschii. The first two steps in the pathway were predicted to be carried out by genes OE1472F and OE1475F, while the 3^rd step follows the canonical pathway involving gene OE1477R. The functions of these genes and their products were tested by biochemical and genetic methods. In this study, we provide evidence that supports the role of proteins OE1472F and OE1475F catalyzing consecutive enzymatic reactions leading to the production of 3-dehydroquinate (DHQ), after which AroAA production proceeds via the canonical pathway starting with the formation of DHS (dehydroshikimate), catalyzed by the product of ORF OE1477R. Nutritional requirements and AroAA uptake studies of the mutants gave results that were consistent with the proposed roles of these ORFs in AroAA biosynthesis. DNA microarray data indicated that the 13 genes of the canonical pathway appear to be utilised for AroAA biosynthesis in H. salinarum, as they are differentially expressed when cells are grown in medium lacking AroAA.     

Polymerization of β-amino Acids in Aqueous Solution

We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged - and -amino acids in homogeneous aqueous solution. -Amino acids can be oligomerized efficiently using CDI, but not by EDAC. -Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an - and -dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.     

Arabidopsis Lipins,PDAT1 Acyltransferase,and SDP1 Triacylglycerol Lipase Synergistically Direct Fatty Acids toward β-Oxidation,Thereby Maintaining Membrane Lipid Homeostasis

Triacylglycerol (TAG) metabolism is a key aspect of intracellular lipid homeostasis in yeast and mammals, but its role in vegetative tissues of plants remains poorly defined. We previously reported that PHOSPHOLIPID:DIACYLGLYCEROL ACYLTRANSFERASE1 (PDAT1) is crucial for diverting fatty acids (FAs) from membrane lipid synthesis to TAG and thereby protecting against FA-induced cell death in leaves. Here, we show that overexpression of PDAT1 enhances the turnover of FAs in leaf lipids. Using the trigalactosyldiacylglycerol1-1 (tgd1-1) mutant, which displays substantially enhanced PDAT1-mediated TAG synthesis, we demonstrate that disruption of SUGAR-DEPENDENT1 (SDP1) TAG lipase or PEROXISOMAL TRANSPORTER1 (PXA1) severely decreases FA turnover, leading to increases in leaf TAG accumulation, to 9% of dry weight, and in total leaf lipid, by 3-fold. The membrane lipid composition of tgd1-1 sdp1-4 and tgd1-1 pxa1-2 double mutants is altered, and their growth and development are compromised. We also show that two Arabidopsis thaliana lipin homologs provide most of the diacylglycerol for TAG synthesis and that loss of their functions markedly reduces TAG content, but with only minor impact on eukaryotic galactolipid synthesis. Collectively, these results show that Arabidopsis lipins, along with PDAT1 and SDP1, function synergistically in directing FAs toward peroxisomal β-oxidation via TAG intermediates, thereby maintaining membrane lipid homeostasis in leaves.     

Studies on γ-Radiolysis of Sulfur Containing Amino Acids

In connection with flavor deterioration accompanied by food irradiation, the effect of γ-irradiation on sulfoxide amino acids in air free aqueous system was investigated. The major radiolysis products from S-n-propyl-l-cysteine sulfoxide (PCSO) were alanine, cysteic acid, dipropyl disulfide, etc., and from S-allyl-l-cysteine sulfoxide (ACSO) were S-allyl-l-cysteine, cystine, cysteic acid, etc., which were isolated chromatographycally and identified by using IR and mass spectrometry. The sulfoxide in ACSO was more easily reduced to sulfide than that of in PCSO, and the bond of S-C (β-carbon in alanine moiety) in ACSO was difficult to cleave. These differences observed between PCSO and ACSO in the radiolysis products and their yields indicate that the radiolysis degradation is considerably influenced by the structure of alkyl group. From the experiments with N₂O or KBr addition during irradiation, principal roles of the active species in irradiated water in the degradation processes were partly elucidated.     

Constitutional Amino Acids of the Antibiotic YA–56

Acid hydrolysis of the antibiotic YA-56 X (Zorbamycin) and Y belonging to the phleomycin-bleomycin group was carried out and the following constitutional amino acids were isolated from the hydrolyzate of YA–56 X: β-Amino-β-(4-amino-6-carboxy-5-methylpyrimidine-2-yl)- propionic acid, β-aminoalanine, L-erythro-β-hydroxyhistidine and 3 unidentified amino acids. Though the former 3 amino acids were known to be constituents of phleomycins and bleomycins, the latter three were not found in phleomycins and bleomycins. YA–56 Y gave one more unidentified amino acid.

Furthermore, isolation of β-alanine and 2-acetylthiazole-4-carboxylic acid from the hydrolyzate indicated the presence of 2-(2-(2-aminoethyl)-Δ²-thiazoline-4-yl)-thiazole-4-carboxylic acid in YA–56 X and Y as in phleomycins.     

The Interrelationship between Polyunsaturated Fatty Acids, α-Tocopherol and Glutathione Peroxidase in Chicken and Porcine Skeletal Muscles

Two species of chrysomelid leaf beetles found in Brazil, Diabrotica speciosa and Cerotoma arcuata, are strongly attracted to the root of Ceratosanthes hilariana (Cucurbitaceae). Root extracts stimulate a compulsive feeding response. The major feeding stimulants isolated from these extracts were cucurbitacin B and its 23,24-dihydro derivative.     

The Preparation and Geometrical Isomerism of Substituted α-Methylthio-Cinnamic Acids

α-Methylthio-cinnamic acid and its substituted analogues (III) were synthesized from their respective β-aryl-α-thiopyruvic acids (II). In connection with the study on the tautomeric ene-thiol structure of β-aryl-α-thiopyruvic acids (II), 4-arylidenerl,3-oxathiolan-5-one (IV) were prepared from compounds II.     

The Preparation and Geometrical Isomerism of Substituted α-Methylthio-cinnamic Acids

Measurements of NMR spectra of β-aryl-α-thiopyruvic acids revealed that they exist dominantly in the form of trans cinnamic acid configuration. Geometrical configuration of 4-arylidene-1,3-oxathiolan-5-one was also determined to be trans in regard to aryl and carbonyl groups.     

β-Branched Amino Acids Stabilize Specific Conformations of Cyclic Hexapeptides

Cyclic peptides (CPs) are a promising class of molecules for drug development, particularly as inhibitors of protein-protein interactions. Predicting low-energy structures and global structural ensembles of individual CPs is critical for the design of bioactive molecules, but these are challenging to predict and difficult to verify experimentally. In our previous work, we used explicit-solvent molecular dynamics simulations with enhanced sampling methods to predict the global structural ensembles of cyclic hexapeptides containing different permutations of glycine, alanine, and valine. One peptide, cyclo-(VVGGVG) or P7, was predicted to be unusually well structured. In this work, we synthesized P7, along with a less well-structured control peptide, cyclo-(VVGVGG) or P6, and characterized their global structural ensembles in water using NMR spectroscopy. The NMR data revealed a structural ensemble similar to the prediction for P7 and showed that P6 was indeed much less well-structured than P7. We then simulated and experimentally characterized the global structural ensembles of several P7 analogs and discovered that β-branching at one critical position within P7 is important for overall structural stability. The simulations allowed deconvolution of thermodynamic factors that underlie this structural stabilization. Overall, the excellent correlation between simulation and experimental data indicates that our simulation platform will be a promising approach for designing well-structured CPs and also for understanding the complex interactions that control the conformations of constrained peptides and other macrocycles.