Metabolism of 3-indoleacetic acid in tobacco exposed to the air pollutant peroxyacetyl nitrate

The influence of an air pollutant, peroxyacetyl nitrate (PAN),on 3-indoleacetic acid (IAA) and its metabolites in tobaccoplants was studied. Plants were administered IAA-2-¹⁴C immediatelybefore or after gassing with PAN. After 8 hr metabolism in thedark or in the light the plants were separated into shoot tipand damaged and undamaged leaf areas prior to analysis. PAN-treatedplants which metabolized in the light and produced partiallydamaged leaves showed a relative increase in unmetabolized IAAin the leaves compared to control treatments. Several suspectedindole conjugates from leaves of PAN-treated plants containedrelatively less label than controls. Plants which metabolizedin the dark and showed no visible external damage also demonstratedchanges in indoleacetic acid metabolism. The changes were qualitativelydifferent however from those observed in damaged tissue. UndamagedPAN-treated tissue consistently had less of certain unidentifiedcompounds. It was concluded that PAN is capable of causing biochemicallesions in indole metabolism prior to the expression of visibledamage. ¹ Present address: Canada department of Agriculture, ResearchBranch, 2560 Chemin Gomin, Ste-Foy, Quebec 10, Canada. (Received June 29, 1971; )     

Structural insights into the regulation of aromatic amino acid hydroxylation

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Regulation of pteridine biosynthesis and aromatic amino acid hydroxylation inDrosophila melanogaster

The relationship between high dietary levels of aromatic amino acid and regulation of pteridines inDrosophila eyes was examined by measuring changes in pool levels of six pterins in the wild type and mutants and amino acid pool levels in flies that carry mutations for pteridine biosynthesis. The effect upon relative viability and developmental times was also analyzed; relative viability was affected byl-phenylalanine,l-tryptophan, andl-tyrosine in decreasing order and thed-amino acids had little or no effect. The changes in concentration of biopterin, dihydrobiopterin, pterin, sepiapterin, drosopterins, and isoxanthopterin showed a characteristic pattern of increased and/or decreased amounts in response to each of the threel-amino acids. Pterin was regularly increased, and isoxanthopterin decreased.l-Tyrosine caused a 2.1-fold increase in dihydrobiopterin, the largest increase found in this study;l-tryptophan also caused dihydrobiopterin to increase butl-phenylalanine did not. Of 18 eye-color mutants examined, 2 were found to contain high levels of phenylalanine and/or tyrosine,Pu ² andHn ^r3. These two mutants, along withpr ^c4 cn/pr ^m2b cn, were shown to be very sensitive to dietaryl-phenylalanine, indicating that having low levels of certain pteridines makes them susceptible to toxic effects of these amino acids. Therefore, high levels of aromatic amino acids can perturb the balance among pteridine pools, and low levels of some pteridines in mutants are correlated with the inability to withstand the toxic effects of phenylalanine. From the patterns of change in the pteridines we suggest that tetrahydropterin may also be a cofactor for hydroxylation of phenylalanine, along with tetrahydrobiopterin.This work was sponsored in part by a grant from the U.S.-Spain Joint Committee for Scientific and Technological Cooperation.     

A physiological and morphological study on the injury caused by exposure to the air pollutant,peroxyacetyl nitrate (PAN), based on the quantitative assessment of the injury

A method for the numerical assessment of the foliar injury caused by the photochemical oxidant, peroxyacetyl nitrate (PAN), was devised, using three injury indices: fresh weight (FW) loss, decreased photosynthetic pigment content, and increased ion leakage, which can be measured using the same leaves. The injury indices clearly indicated a larger number of PAN-sensitive leaves and a more severe level of injury in the PAN-sensitive variety of Petunia hybrida, White Champion (WHITE), compared to the PAN-tolerant variety, Blue Champion (BLUE). FW and photosynthetic pigment content decreased correlatively in both varieties, but ion leakage increased only in WHITE. Morphological observations revealed that ion leakage started concurrently with the start of plasmolysis-like symptoms at the mesophyll cells of injured WHITE leaves, whereas FW loss corresponded to the shrinkage of cells without loss of their round shape in BLUE leaves. PAN injuries measured by the injury indices were markedly increased in the presence of light, and the morphological changes following PAN exposure were similar to those caused by the superoxide-generating chemical, paraquat. The results suggested that PAN injuries indicated by the three injury indices are all light-dependent, but are caused through several independent mechanisms.     

Mutagenicity in lung of Big Blue mice and induction of tandem-base substitutions in Salmonella by the air pollutant peroxyacetyl nitrate (PAN): predicted formation of intrastrand cross-links

Peroxyacetyl nitrate (PAN) is a ubiquitous air pollutant formed from NO₂ reacting with acetoxy radicals generated from ambient aldehydes in the presence of sunlight and ozone. It contributes to eye irritation associated with photochemical smog and is present in most urban air. PAN was generated in a chamber containing open petri dishes of Salmonella TA100 (gas-phase exposure). After subtraction of the background mutation spectrum, the spectrum of PAN-induced mutants selected at 3.1-fold above the background mutant yield was 59% GC→TA, 29% GC→AT, 2% GC→CG, and 10% multiple mutations — primarily GG→TT tandem-base substitutions. Using computational molecular modeling methods, a mechanism was developed for producing this unusual tandem-base substitution. The mechanism depends on the protonation of PAN near the polyanionic DNA to release NO₂⁺ resulting in intrastrand dimer formation. Insertion of AA opposite the dimerized GG would account for the tandem GG→TT transversions. Nose-only exposure of Big Blue^® mice to PAN at 78 ppm (near the MTD) was mutagenic at the lacI gene in the lung (mutant frequency ±S.E. of 6.16±0.58/10⁵ for controls versus 8.24±0.30/10⁵ for PAN, P=0.016). No tandem-base mutations were detected among the 40 lacI mutants sequenced. Dosimetry with ³H-PAN showed that 24 h after exposure, 3.9% of the radiolabel was in the nasal tissue, and only 0.3% was in the lung. However, based on the molecular modeling considerations, the labeled portion of the molecule would not have been expected to have been bound covalently to DNA. Our results indicate that PAN is weakly mutagenic in the lungs of mice and in Salmonella and that PAN produces a unique signature mutation (a tandem GG→TT transversion) in Salmonella that is likely due to a GG intrastrand cross-link. Thus, PAN may pose a mutagenic and possible carcinogenic risk to humans, especially at the high concentrations at which it is present in some urban environments.     

疏水性氨基酸的羟基化研究进展

羟基化氨基酸在生物技术和分子生物学中具有独特价值,具有抗真菌、抗菌、抗病毒和抗癌的特性。通过比较化学合成与生物催化合成羟基氨基酸的异同,选择具有高对映结构选择性的生物催化合成方法成为羟基氨基酸合成的首选。生物催化实现疏水性氨基酸的羟基化和羟化酶紧密相关,而羟化酶又是单核非血红素Fe(Ⅱ)和α-酮戊二酸依赖型双加氧酶(Fe/αKGDs)的一种,Fe/αKGDs存在共性催化机制。因此,疏水性氨基酸在被催化的过程中,会利用关键中间体高价铁-超氧复合体(Fe(Ⅳ)=O)引起多种氧化转化,从而完成羟基化过程。文中就疏水性氨基酸的羟基化合成及功能应用,尤其是(2S,3R,4S)-4-羟基-异亮氨酸(4-HIL)和羟脯氨酸,进行了详细的阐述,探讨了Fe/αKGDs的共性催化反应机制,并对羟基氨基酸在基础研究和工业中的应用进行了综述。     

Mutagenicity in lung of big Blue((R)) mice and induction of tandem-base substitutions in Salmonella by the air pollutant peroxyacetyl nitrate (PAN): predicted formation of intrastrand cross-links

Peroxyacetyl nitrate (PAN) is a ubiquitous air pollutant formed from NO(2) reacting with acetoxy radicals generated from ambient aldehydes in the presence of sunlight and ozone. It contributes to eye irritation associated with photochemical smog and is present in most urban air. PAN was generated in a chamber containing open petri dishes of Salmonella TA100 (gas-phase exposure). After subtraction of the background mutation spectrum, the spectrum of PAN-induced mutants selected at 3.1-fold above the background mutant yield was 59% GC-->TA, 29% GC-->AT, 2% GC-->CG, and 10% multiple mutations - primarily GG-->TT tandem-base substitutions. Using computational molecular modeling methods, a mechanism was developed for producing this unusual tandem-base substitution. The mechanism depends on the protonation of PAN near the polyanionic DNA to release NO(2)(+) resulting in intrastrand dimer formation. Insertion of AA opposite the dimerized GG would account for the tandem GG-->TT transversions. Nose-only exposure of Big Blue((R)) mice to PAN at 78ppm (near the MTD) was mutagenic at the lacI gene in the lung (mutant frequency +/-S.E. of 6.16+/-0.58/10(5) for controls versus 8.24+/-0.30/10(5) for PAN, P=0.016). No tandem-base mutations were detected among the 40 lacI mutants sequenced. Dosimetry with 3H-PAN showed that 24h after exposure, 3.9% of the radiolabel was in the nasal tissue, and only 0.3% was in the lung. However, based on the molecular modeling considerations, the labeled portion of the molecule would not have been expected to have been bound covalently to DNA. Our results indicate that PAN is weakly mutagenic in the lungs of mice and in Salmonella and that PAN produces a unique signature mutation (a tandem GG-->TT transversion) in Salmonella that is likely due to a GG intrastrand cross-link. Thus, PAN may pose a mutagenic and possible carcinogenic risk to humans, especially at the high concentrations at which it is present in some urban environments.     

Phylogenetic analysis and evolution of aromatic amino acid hydroxylase

A study was performed to investigate the phylogenetic relationship among AAAH members and to statistically evaluate sequence conservation and functional divergence. In total, 161 genes were identified from 103 species. Phylogenetic analysis showed that well-conserved subfamilies exist. Exon-intron structure analysis showed that the gene structures of AAAH were highly conserved across some different lineage species, while some species-specific introns were also found. The dynamic distribution of ACT domain suggested one gene fusion event has occurred in eukaryota. Significant functional divergence was found between some subgroups. Analysis of the site-specific profiles revealed critical amino acid residues for functional divergence. This study highlights the molecular evolution of this family and may provide a starting point for further experimental verifications.     

Reaction of peroxyacetyl nitrate with cysteine,cystine, methionine,lipoic acid,papain, and lysozyme

Peroxyacetyl nitrate was reactive with small molecular-weight sulfur-containing compounds The order of susceptibility was cysteine > reduced lipoic acid = reduced lipoamide > oxidized lipoic acid > oxidized lipoamide > methionine ? cystine. From thiols the predominant product was disulfide. In the early stages of oxidation methionine yielded methionine sulfoxide. Products of oxidation of oxidized lipoic acid and lipoamide were the respective sulfoxides. Cystine was resistant to oxidation, yielding cysteic acid when oxidation took place.Papain was readily inactivated by peroxyacetyl nitrate while lysozyme was resistant. The small amount of inactivation of lysozyme was correlated with methionine oxidation. Papain inactivation was correlated with thiol oxidation and could be reversed by thiol compounds. The oxidation product was judged to be a dimer by methods for determining molecular weight.     

Indoor/outdoor concentrations of ozone and peroxyacetyl nitrate (PAN)

 Photochemical pollutants such as ozone and peroxyacetyl nitrate (PAN) could adversely affect human health, especially with relation to effects on lung function. For a realistic assessment of ambient concentrations, both outdoor and indoor measurements of ozone and PAN are required, because people stay indoors for most of the time. Indoor/outdoor concentration ratios, indoor half-life times and indoor chemistry including physicochemical reactions on surfaces are quite well known for ozone, but not for PAN. While ozone is removed very rapidly mainly by heterogeneous reactions on surfaces or by gasphase reactions with e.g. carpet emissions, no such processes are known for PAN at present. The main removal process for PAN is thermal decay. Indoor concentrations of ozone and PAN can be a significant fraction of those outdoors highly depending on the ventilation pattern. Our measurements in various kinds of non-air-conditioned rooms show maximal indoor concentrations between 80 and 100% of those outdoors for ozone and PAN, respectively. Average indoor/outdoor ratios were calculated of 0.5 for ozone and between 0.7 and 0.9 for PAN. The half-life times ranged between only a few minutes for ozone and 0.5 to 1 h for PAN. Received: 11 December 1996 / Accepted: 24 January 1997     

Modification of hyaluronic acid with aromatic amino acids

Hyaluronic acid was modified with aromatic amino acids (5-aminosalicylic, 4-aminosalicylic, anthranilic, and p-aminobenzoic) in the presence of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The modified glycans contained 9-43% of arylamide groups and 10-33% of isoureidocarbonyl groups depending on the nature of the amino acid. Reduction with sodium borohydride allowed the conversion of isoureidocarbonyl groups into hydroxymethyl groups.     

Modification of hyaluronic acid with aromatic amino acids

Hyaluronic acid was modified with aromatic amino acids (5-aminosalicylic, 4-aminosalicylic, anthranilic, and p-aminobenzoic) in the presence of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. The modified glycans contained 9–43% of arylamide groups and 10–33% of isoureidocarbonyl groups depending on the nature of the amino acid. Reduction with sodium borohydride allowed the conversion of isoureidocarbonyl groups into hydroxymethyl groups.Translated from Bioorganicheskaya Khimiya, Vol. 31, No. 1, 2005, pp. 90–95.Original Russian Text Copyright © 2005 by Ponedelkina, Odinokov, Vakhrusheva, Golikova, Khalilov, Dzhemilev.