The effect of AmtR on growth and amino acids production in Corynebacterium glutamicum

AmtR, the master regulator of nitrogen control in Corynebacterium glutamicum, plays important roles in nitrogen metabolism. To investigate the influence of AmtR on amino acids production in C. glutamicum ATCC 13032, the amtR deletion strain C. glutamicum Q1 was constructed and cultured in modified CGXII minimal medium for 60 h. The ammonium consumption rates as well as amino acids production of both strains cultured in modified CGXII minimal medium were determined. The amtR deletion in C. glutamicum caused an obvious growth defect in the exponential growth phase, but both strains had the same biomass in the stationary phases. Maybe the less alpha-oxoglutarate was used for the tricarboxylic acid cycle to influence the growth of strains. During 12 h, the rate of ammonium consumption and the concentration of Glu, Pro, Arg and Ser were higher but Asp, Gly, Ile, Leu, Lys were lower in the mutation strain. During 48 h, the Q1 had higher levels of Asp, Lys, Pro, Ala and Val,and lower levels of Glu, Arg, Leu and Ile, compared to the wild. The more Glu was synthesized by the activated GS/GOGAT pathway in Q1, and then the accumulation of relative amino acids (Pro, Arg and Ser) were up-regulated within 12 h growth. After 48 h growth, the amtR deletion obviously influenced accumulation of Ala, Asp and Pro. The amtR deletion could influence the growth and amino acids production, which could be useful to the production of amino acids.     

DNA binding by Corynebacterium glutamicum TetR-type transcription regulator AmtR

Background  

The TetR family member AmtR is the central regulator of nitrogen starvation response in Corynebacterium glutamicum. While the AmtR regulon was physiologically characterized in great detail up to now, mechanistic questions of AmtR binding were not addressed. This study presents a characterization of functionally important amino acids in the DNA binding domain of AmtR and of crucial nucleotides in the AmtR recognition motif.     

The primary structure of the COOH-terminal half of cholera toxin subunit A1 containing the ADP-ribosylation site

The sequence of 96 amino acid residues from the COOH-terminus of the active subunit of cholera toxin, A₁, has been determined as PheAsnValAsnAspVal LeuGlyAlaTyrAlaProHisProAsxGluGlu GluValSerAlaLeuGlyGly IleProTyrSerGluIleTyrGlyTrpTyrArg ValHisPheGlyValLeuAsp GluGluLeuHisArgGlyTyrArgAspArgTyr TyrSerAsnLeuAspIleAla ProAlaAlaAspGlyTyrGlyLeuAlaGlyPhe ProProGluHisArgAlaTrp ArgGluGluProTrpIleHisHisAlaPro ProGlyCysGlyAsnAlaProArg(OH). This is the largest fragment obtained by BrCN cleavage of the subunit A₁ (M_r 23,000), and has previously been indicated to contain the active site for the adenylate cyclase-stimulating activity. Unequivocal identification of the COOH-terminal structure was achieved by separation and analysis of the terminal peptide after the specific chemical cleavage at the only cysteine residue in A₁ polypeptide. The site of self ADP-ribosylation in the A₁ subunit [C. Y. Lai, Q.-C. Xia, and P. T. Salotra (1983) Biochem. Biophys. Res. Commun.116, 341–348] has now been identified as Arg-50 of this peptide, 46 residues removed from the COOH-terminus. The cysteine that forms disulfide bridge to A₂ subunit in the holotoxin is at position 91.     

The primary structure of the β-subunit of protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa

The complete amino acid sequence of the β-subunit of protocatechuate 3,4-dioxygenase was determined. The β-subunit contained four methionine residues. Thus, five peptides were obtained after cleavage of the carboxymethylated β-subunit with cyanogen bromide, and were isolated on Sephadex G-75 column chromatography. The amino acid sequences of the cyanogen bromide peptides were established by characterization of the peptides obtained after digestion with trypsin, chymotrypsin, thermolysin, or Staphylococcus aureus protease. The major sequencing techniques used were automated and manual Edman degradations. The five cyanogen bromide peptides were aligned by means of the amino acid sequences of the peptides containing methionine purified from the tryptic hydrolysate of the carboxymethylated β-subunit. The amino acid sequence of all the 238 residues was as follows: ProAlaGlnAspAsnSerArgPheValIleArgAsp ArgAsnTrpHis ProLysAlaLeuThrPro-Asp — TyrLysThrSerIleAlaArg SerProArgGlnAla LeuValSerIleProGlnSer — IleSerGluThrThrGly ProAsnPheSerHisLeu GlyPheGlyAlaHisAsp-His — AspLeuLeuLeuAsnPheAsn AsnGlyGlyLeu ProIleGlyGluArgIle-Ile — ValAlaGlyArgValValAsp GlnTyrGlyLysPro ValProAsnThrLeuValGluMet — TrpGlnAlaAsnAla GlyGlyArgTyrArg HisLysAsnAspArgTyrLeuAlaPro — LeuAspProAsn PheGlyGlyValGly ArgCysLeuThrAspSerAspGlyTyrTyr — SerPheArg ThrIleLysProGlyPro TyrProTrpArgAsnGlyProAsnAsp — TrpArgProAla HisIleHisPheGlyIle SerGlyProSerIleAlaThr-Lys — LeuIleThrGlnLeuTyr PheGluGlyAspPro LeuIleProMetCysProIleVal — LysSerIleAlaAsn ProGluAlaValGlnGln LeuIleAlaLysLeuAspMetAsnAsn — AlaAsnProMet AsnCysLeuAlaTyr ArgPheAspIleValLeuArgGlyGlnArgLysThrHis PheGluAsnCys. The sequence published earlier in summary form (Iwaki et al., 1979, J. Biochem.86, 1159–1162) contained a few errors which are pointed out in this paper.     

Amino acid sequence of seminalplasmin, an antimicrobial protein from bull semen

Analytical ultracentrifugation of highly purified seminalplasmin revealed a molecular mass of 6300. Amino acid analysis of the protein preparation indicated the absence of sulfur-containing amino acids cysteine and methionine. The amino acid sequence of seminalplasmin was determined by manual Edman degradation of peptides obtained by proteolytic enzymes trypsin, chymotrypsin and thermolysin: NH₂-Ser Asp Glu Lys Ala Ser Pro Asp Lys His His Arg Phe Ser Leu Ser Arg Tyr Ala Lys Leu Ala Asn Arg Leu Ser Lys Trp Ile Gly Asn Arg Gly Asn Arg Leu Ala Asn Pro Lys Leu Leu Glu Thr Phe Lys Ser Val-COOH. The number of amino acids according to the sequence were 48, the molecular mass 6385. As predicted from the sequence, seminalplasmin very likely contains two α-helical domains in which residues 8-17 and 40-48 are involved. No evidence for the existence of β-sheet structures was obtained. Treatment of seminalplasmin with the above proteases as well as with amino peptidase M and carboxypeptidase Y completely eliminated biological activity.     

不同产区太子参氨基酸含量测定及多元统计分析

本文采用高速氨基酸自动分析仪对太子参四大种植主产区(安徽、江苏、福建、贵州)的栽培品及河南的野生品,共13个批次太子参药材的氨基酸组成和含量进行测定。结果显示氨基酸含量基本顺序为:精氨酸(Arg)>谷氨酸(Glu)>天冬氨酸(Asp)>脯氨酸(Pro),其中安徽宣城产太子参样品(S2)的16种氨基酸总含量和7种人体必需氨基酸含量最高。以上述4种主要氨基酸作为指标,探讨了不同产区太子参药材的内在品质。采用聚类分析法对氨基酸含量进行多元统计分析,表明氨基酸含量分析可体现样品产区间和产区内的差异性,可区别野生品与栽培品。这些结果为发展太子参道地药材的质量标准控制提供了依据。     

Purification and structure analysis of mycolic acids in <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Corynebacterium glutamicum is widely used for producing amino acids. Mycolic acids, the major components in the cell wall of C. glutamicum might be closely related to the secretion of amino acids. In this study, mycolic acids were extracted from 5 strains of C. glutamicum, including ATCC 13032, ATCC 13869, ATCC 14067, L-isoleucine producing strain IWJ-1, and L-valine producing strain VWJ-1. Structures of these mycolic acids were analyzed using thin layer chromatography and electrospray ionization mass spectrometry. More than twenty molecular species of mycolic acid were observed in all 5 strains. They differ in the length (20–40 carbons) and saturation (0–3 double bonds) of their constituent fatty acids. The dominant species of mycolic acid in every strain was different, but their two hydrocarbon chains were similar in length (14–18 carbons), and the meromycolate chain usually contained double bonds. As the growth temperature of cells increased from 30°C to 34°C, the proportion of mycolic acid species containing unsaturated and shorter hydrocarbon chains increased. These results provide new information on mycolic acids in C. glutamicum, and could be useful for modifying the cell wall to increase the production of amino acids.     

Significance of Extracellular Protease for Growth of a Heterotrophic Bacterium, Aeromonas salmonicida

The role of protease produced by a heterotrophic bacterium during growth was investigated with Aeromonas salmonicida, the pathogen of fish furunculosis, strain A-7301 and its protease-deficient mutant NTG-1 induced by mutagenesis. Strain A-7301 produced extracellular protease in a mixed amino acid medium (composed of Gly, Ala, Val, Ile, Leu, Thr, Ser, Cys, Met, Phe, Tyr, Lys, Arg, Pro, His, Try, Asp, Asn, Glu, and Gln at equal concentrations of 0.1 g/liter). Its multiplication rate was limited by the amounts of amino acids present, whereas strain NTG-1 showed no protease production despite considerable growth similar to that of A-7301. There was no difference between A-7301 and NTG-1 in amino acid requirements for growth, and seven amino acids (Gly, Ala, Val, Thr, Cys, Met, and His) were found to be indispensable. A defined level of the mixed amino acids (0.4 to 0.5 g/liter) was needed for A-7301 to initiate a large production of protease. Neither of the strains grew well in a casein medium, to which no amino acids were added. However, when a protease fraction obtained from extracellular products of A-7301 by DEAE-cellulose column chromatography was added, NTG-1 successfully reproduced in the casein medium. These results indicate that the extracellular protease plays an important role in supplying A. salmonicida cells with available amino acids as nutrients and that higher growth is closely associated with protease production which stimulates further reproduction.     

A genome-wide association study reveals that the 2-oxoglutarate/malate translocator mediates seed vigor in rice

Seed vigor is an important trait for the direct seeding of rice (Oryza sativa L.). In this study, we examined the genetic architecture of variation in the germination rate using a diverse panel of rice accessions. Four quantitative trait loci for germination rate were identified using a genome-wide association study during early germination. One candidate gene, encoding the 2-oxoglutarate/malate translocator (OsOMT), was validated for qGR11. Disruption of this gene (Osomt mutants) reduced seed vigor, including seed germination and seedling growth, in rice. Functional analysis revealed that OsOMT influences seed vigor mainly by modulating amino acid levels and glycolysis and tricarboxylic acid cycle processes. The levels of most amino acids, including the Glu family (Glu, Pro, Arg, and GABA), Asp family (Asp, Thr, Lys, Ile, and Met), Ser family (Ser, Gly, and Cys), and others (His, Ala, Leu, and Val), were significantly reduced in the mature grains and the early germinating seeds of Osomt mutants compared to wild type (WT). The glucose and soluble sugar contents, as well as adenosine triphosphate levels, were significantly decreased in germinating seeds of Osomt mutants compared to WT. These results provide important insights into the role of OsOMT in seed vigor in rice.     

Probing the structure-activity relationship of Escherichia coli LT-A by site-directed mutagenesis

Computer analysis of the crystallographic structure of the A subunit of Escherichia coil heat-labile toxin (LT) was used to predict residues involved in NAD binding, catalysis and toxicity. Following site-directed mutagenesis, the mutants obtained could be divided into three groups. The first group contained fully assembled, non-toxic new molecules containing mutations of single amino acids such as Val-53 → Glu or Asp, Ser-63 → Lys, Val-97 → Lys, Tyr-104 → Lys or Asp, and Ser-14 → Lys or Glu. This group also included mutations in amino acids such as Arg-7, Glu-110 and Glu-112 that were already known to be important for enzymatic activity. The second group was formed by mutations that caused the collapse or prevented the assembly of the A subunit: Leu-41 → Phe, Ala-45 → Tyr or Glu, Val-53 → Tyr, Val-60 → Gly, Ser-68 → Pro, His-70 → Pro, Val-97 → Tyr and Ser-114 → Tyr. The third group contained those molecules that maintained a wild-type level of toxicity in spite of the mutations introduced: Arg-54 → Lys or Ala, Tyr-59 → Met, Ser-68 → Lys, Ala-72 → Arg, His or Asp and Arg-192 → Asn. The results provide a further understanding of the structure–function of the active site and new, non-toxic mutants that may be useful for the development of vaccines against diarrhoeal diseases.     

Differentiation of the photosynthetic apparatus of Chloroflexus aurantiacus depending on growth with different amino acids

The phototrophic green bacterium Chloroflexus aurantiacus was grown anaerobically in batch culture with different amino acids at 56°C and constant illumination of 25 klx. The composition of the photosynthetic apparatus was measured by quantitation of the bacteriochlorophylls (Bchl) a and c (representing the membrane-bound and the chlorosomal moieties, respectively). Ser added at concentrations up to 15 mM stimulated protein formation and Bchl a and c syntheses. A comparable stimulation was found with Glu and Ala. Coproporphyrin accumulation approached saturation at 5 mM of Ala, Asp, Orn, and Ser, while with Glu and Arg saturating concentrations were above 5 mM. Protein and tetrapyrrole syntheses became saturated at 2.5 to 5 mM of Asp, Ile, and Val. However, with Arg and Orn Bchl c synthesis was stimulated up to 2.5 mM, growth and Bchl a synthesis up to 5 mM. At higher Arg or Orn concentrations these activities were inhibited. Coproporphyrin accumulation was highest with Arg or Orn, at concentrations which inhibited growth and Bchl formation. Stimulation of Bchl synthesis took place preferentially at the level of Bchl c, while Bchl a was more sensitive toward inhibition. In both cases however, the ratio of Bchl c to Bchl a increased with higher amino acid concentrations. Nevertheless, each amino acid induced a typical effect. To understand different effects exerted by different amino acids, chemostat cultures were grown limited by either Ser or Glu. With Ser, steady state protein levels and specific Bchl a contents decreased slightly when increasing the dilution rate (D). Concomitantly Bchl c and coproporphyrin levels as well as the ratio of Bchl a/Bchl c increased. With Glu as the limiting substrate, all of the above mentioned parameters decreased. Since all of the Ser was consumed and increasing amounts of Glu remained unutilized in the spent medium, it is concluded that differences in the formation of the three pyrrole derivatives tested are due to differences in the affinities of uptake systems for Ser and Glu.     

Purification of amoebolytic substances from Bacillus licheniformis M-4

Three antibiotic peptides with amoebolytic activity have been purified from culture supernatants of Bacillus licheniformis M-4 (amoebicins m4-A, m4-B, and m4-C). They were hydrophilic peptides consisting of six different amino acids (Asp, Glu, Ser, Thr, Pro, Tyr). Their molecular weights ranged from 3,000 to 3,200. Purified amoebicins were active against human pathogenic and non-pathogenic strains of Naegleria. They also showed a broad antifungal spectrum, but a narrow antibacterial activity.Abbreviations (TFA) Trifluoroacetic acid     

Uptake of Amino Acids and Their Metabolic Conversion into the Compatible Solute Proline Confers Osmoprotection to Bacillus subtilis

The data presented here reveal a new facet of the physiological adjustment processes through which Bacillus subtilis can derive osmostress protection. We found that the import of proteogenic (Glu, Gln, Asp, Asn, and Arg) and of nonproteogenic (Orn and Cit) amino acids and their metabolic conversion into proline enhances growth under otherwise osmotically unfavorable conditions. Osmoprotection by amino acids depends on the functioning of the ProJ-ProA-ProH enzymes, but different entry points into this biosynthetic route are used by different amino acids to finally yield the compatible solute proline. Glu, Gln, Asp, and Asn are used to replenish the cellular pool of glutamate, the precursor for proline production, whereas Arg, Orn, and Cit are converted into γ-glutamic semialdehyde/Δ¹-pyrroline-5-carboxylate, an intermediate in proline biosynthesis. The import of Glu, Gln, Asp, Asn, Arg, Orn, and Cit did not lead to a further increase in the size of the proline pool that is already present in osmotically stressed cells. Hence, our data suggest that osmoprotection of B. subtilis by this group of amino acids rests on the savings in biosynthetic building blocks and energy that would otherwise have to be devoted either to the synthesis of the proline precursor glutamate or of proline itself. Since glutamate is the direct biosynthetic precursor for proline, we studied its uptake and found that GltT, an Na⁺-coupled symporter, is the main uptake system for both glutamate and aspartate in B. subtilis. Collectively, our data show how effectively B. subtilis can exploit environmental resources to derive osmotic-stress protection through physiological means.     

Amino acid sequence of a protease inhibitor isolated from Sarcophaga bullata determined by mass spectrometry.

The amino acid sequence of a protease inhibitor isolated from the hemolymph of Sarcophaga bullata larvae was determined by tandem mass spectrometry. Homology considerations with respect to other protease inhibitors with known primary structures assisted in the choice of the procedure followed in the sequence determination and in the alignment of the various peptides obtained from specific chemical cleavage at cysteines and enzyme digests of the S. bullata protease inhibitor. The resulting sequence of 57 residues is as follows: Val Asp Lys Ser Ala Cys Leu Gln Pro Lys Glu Val Gly Pro Cys Arg Lys Ser Asp Phe Val Phe Phe Tyr Asn Ala Asp Thr Lys Ala Cys Glu Glu Phe Leu Tyr Gly Gly Cys Arg Gly Asn Asp Asn Arg Phe Asn Thr Lys Glu Glu Cys Glu Lys Leu Cys Leu.     

The amino acid sequence of human chorionic gonadotropin. The alpha subunit and beta subunit.

The amino acid sequences of both the alpha and beta subunits of human chorionic gonadotropin have been determined. The amino acid sequence of the alpha subunit is: Ala - Asp - Val - Gln - Asp - Cys - Pro - Glu - Cys-10 - Thr - Leu - Gln - Asp - Pro - Phe - Ser - Gln-20 - Pro - Gly - Ala - Pro - Ile - Leu - Gln - Cys - Met - Gly-30 - Cys - Cys - Phe - Ser - Arg - Ala - Tyr - Pro - Thr - Pro-40 - Leu - Arg - Ser - Lys - Lys - Thr - Met - Leu - Val - Gln-50 - Lys - Asn - Val - Thr - Ser - Glu - Ser - Thr - Cys - Cys-60 - Val - Ala - Lys - Ser - Thr - Asn - Arg - Val - Thr - Val-70 - Met - Gly - Gly - Phe - Lys - Val - Glu - Asn - His - Thr-80 - Ala - Cys - His - Cys - Ser - Thr - Cys - Tyr - Tyr - His-90 - Lys - Ser. Oligosaccharide side chains are attached at residues 52 and 78. In the preparations studied approximately 10 and 30% of the chains lack the initial 2 and 3 NH2-terminal residues, respectively. This sequence is almost identical with that of human luteinizing hormone (Sairam, M. R., Papkoff, H., and Li, C. H. (1972) Biochem. Biophys. Res. Commun. 48, 530-537). The amino acid sequence of the beta subunit is: Ser - Lys - Glu - Pro - Leu - Arg - Pro - Arg - Cys - Arg-10 - Pro - Ile - Asn - Ala - Thr - Leu - Ala - Val - Glu - Lys-20 - Glu - Gly - Cys - Pro - Val - Cys - Ile - Thr - Val - Asn-30 - Thr - Thr - Ile - Cys - Ala - Gly - Tyr - Cys - Pro - Thr-40 - Met - Thr - Arg - Val - Leu - Gln - Gly - Val - Leu - Pro-50 - Ala - Leu - Pro - Gin - Val - Val - Cys - Asn - Tyr - Arg-60 - Asp - Val - Arg - Phe - Glu - Ser - Ile - Arg - Leu - Pro-70 - Gly - Cys - Pro - Arg - Gly - Val - Asn - Pro - Val - Val-80 - Ser - Tyr - Ala - Val - Ala - Leu - Ser - Cys - Gln - Cys-90 - Ala - Leu - Cys - Arg - Arg - Ser - Thr - Thr - Asp - Cys-100 - Gly - Gly - Pro - Lys - Asp - His - Pro - Leu - Thr - Cys-110 - Asp - Asp - Pro - Arg - Phe - Gln - Asp - Ser - Ser - Ser - Ser - Lys - Ala - Pro - Pro - Pro - Ser - Leu - Pro - Ser-130 - Pro - Ser - Arg - Leu - Pro - Gly - Pro - Ser - Asp - Thr-140 - Pro - Ile - Leu - Pro - Gln. Oligosaccharide side chains are found at residues 13, 30, 121, 127, 132, and 138. The proteolytic enzyme, thrombin, which appears to cleave a limited number of arginyl bonds, proved helpful in the determination of the beta sequence.     

The Influence of Salinity Acclimation on Free Amino Acids and Enzyme Activities in the Intestinal Mucosa of Rainbow Trout,Oncorhynchus mykiss (Walbaum)

Postprandial changes of Arg, Leu, Val, Ala, Asp, Glu, Gly, Pro and Tau as well as activities of three enzymes of the transdeamination system in the midgut mucosa and, for comparison, in the liver of freshwater and seawater acclimated Oncorhynchus mykiss were studied. In the mucosa a postprandial increase of Arg, Leu, Val, Ala, Asp, Glu, Gly and Pro occurred. In contrast, only the postprandial Arg level increased strongly in the liver. Levels of Leu, Val, Ala, Asp, Glu, Gly, Pro and Tau remained stable. Concentrations of Ala, Asp, Glu and Pro are higher in the liver than the mucosa. Tau is the most important osmotic effector in both organs, but its concentration is much lower in the liver. Its postprandial concentrations remained stable in both tissues but were significantly higher in seawater trout. The trend of a stronger postprandial rise of Arg, Leu, Val, Ala, Asp, Glu, Gly and Pro levels in seawater trout than in freshwater trout was shown. In mucosa tissue aspartate aminotransferase activities were higher in seawater trout. Ratios of aspartate aminotransferase, alanine aminotransferase and glutamate dehydrogenase are similar to those of the gills.     

Salinization and wastewater effects on the growth and some cell contents of Scenedesmus bijugatus

The aim of this study is to determine the effect of salinization and wastewater stresses on the growth, some cellular contents (total soluble proteins, total soluble carbohydrates, nucleic acids, and amino acids composition) and ultrastructure using TEM of unicellular green alga Scenedesmus bijugatus. Treatment of S. bijugatus by NaCl at 10 and 50 mg L⁻¹ significantly increased the growth of this alga and its cellular macro-molecules. While, treatment above this concentration with NaCl significantly inhibited the growth and cellular macro-molecules. On the other hand, treatment by NaCl at the pre-lethal concentration (300 mg L⁻¹) had different effects on its detected amino acids. Whereas, Asp. Acid, Pro, Cys, Val, Iso-leu, leu, Phe.ala and Lys were slightly stimulated with salinization treatment. On contrast the levels of amino acids: Thr, Ser, Glu.acid, Gly, Ala, Mth, His and Arg were markedly inhibited. Ultrastructure examination of treated S. bijugatus by 300 mg L⁻¹ of NaCl for 8 days showed increase of starch granules, shrinkage of cell contents and thickening of cell wall. The recorded data indicated also that treatment by wastewater with all concentrations led to stimulatory effects on their growth and cellular macro-molecules except at 100% wastewater which had inhibitory effects on Asp., Gly., Thr., Ser., Pro., Glu., Ala., Meth., and Cyst., of S. bijugatus. Also, wastewater induced a slight change in the treated S. bijugatus as elevation in starch granules and presence of thylakoid membranes although not clear as in the control.     

TheamrG1 gene is involved in the activation of acetate inCorynebacterium glutamicum

During growth ofCorynebacterium glutamicum on acetate as its carbon and energy source, the expression of theptaack operon is induced, coding for the acetate-activating enzymes, which are phosphotransacetylase (PTA) and acetate kinase (AK). By transposon rescue, we identified the two genesamrG1 andamrG2 found in the deregulated transposon mutant C.glutamicum G25. TheamrG1 gene (NCBI-accession: AF532964) has a size of 732 bp, encoding a polypeptide of 243 amino acids and apparently is partially responsible for the regulation of acetate metabolism in C.glutamicum. We constructed an in-frame deletion mutant and an overexpressing strain ofamrG1 in the C.glutamicum ATCC13032 wildtype. The strains were then analyzed with respect to their enzyme activities of PTA and AK during growth on glucose, acetate and glucose or acetate alone as carbon sources. Compared to the parental strain, theamrG1 deletion mutant showed higher specific AK and PTA activities during growth on glucose but showed the same high specific activities of AK and PTA on medium containing acetate plus glucose and on medium containing acetate. In contrast to the gene deletion, overexpression of theamrG1 gene in C.glutamicum 13032 had the adverse regulatory effect. These results indicate that theamrG1 gene encodes a repressor or co-repressor of theptaack operon.     

Effects of Ceramics Irradiation on Dissociation State of L-Amino Acids

Non-thermal effects of ceramics irradiation on dissociation state of twenty L-amino acids have been investigated. Dissociation constants of the amino acids other than His and Glu varied by a 3-h irradiation under cooling. pK’s of α-carboxyl group of amino acids having longer side chains on the α-carbon were decreased by the irradiation. Although pK’s of α-amino group of Arg, Lys, Asp, and CySH were decreased by the irradiation and pK of Tyr was increased, pK’s of the other fifteen amino acids were not affected. Although the isoelectric points of Lys, Arg, Trp, Asp, and CySH were decreased by the irradiation, those of the other fifteen amino acids were not affected. It was suggested that various changes in pH of amino acids in aqueous solution and dissociation state of the functional groups will be caused from stimulation by the irradiation and stabilization of the hydration layer around amino acids.