Search PubMed⌕ Search

Biomedical subjects

I Chibata

Publications and source records attributed to I Chibata.

At least 19 recordsLinked to original sources
PubMed1999

Proposed standard for human blood vitamin B1 value using HPLC. The Committee for Vitamin Laboratory Standards, Japan.

Standard reference ranges for all laboratory test values are mandatory. This study was designed to establish a reference range for blood vitamin B1 levels, since the normal range has not been determined in the Japanese population. We founded the Japan Committee for Vitamin Laboratory Standards, which was incorporated with the Vitamin Society of Japan and the Japanese Society of Nutrition and Food Science. We standardized whole blood vitamin B1 levels using three HPLC techniques (post-column reverse-phase HPLC, pre-column reverse-phase HPLC, and precolumn GP-HPLC). The reference range was obtained in 54 volunteers administered a 1,800 kcal diet with 2 mg of vitamin B1 (1.74 mg measured) daily to avoid marginal vitamin B1 deficiency in the population. The range for each assay was 26-47, 28-51, and 28-56 ng/ml, respectively. Our data suggest that 26-28 ng/ml is the lower limit of normal for whole blood vitamin B1, but further studies in a larger population are needed in order to obtain more definitive results.

Chromatography, High Pressure Liquid↗
PubMed1983

Characteristics of immobilized histamine for pyrogen adsorption.

The characteristics of immobilized histamine for pyrogen adsorption were investigated. The adsorbent showed a high affinity for pyrogen at low ionic strength, at around neutral pH, at high temperature and at low flow-rates of a solution containing pyrogen. The adsorption capacity per millilitre of the adsorbent was 0.9 mg pyrogen. Immobilized histamine could be completely regenerated by washing with 0.2 M sodium hydroxide solution containing 10--30% ethanol followed by 1.5 M sodium chloride solution, or 0.2 M sodium hydroxide solution followed by 0.5% sodium deoxycholate solution, 0.2 M sodium hydroxide solution and 1.5 M sodium chloride solution.

Chromatography, Agarose↗
PubMed1983

Purification of high molecular weight urokinase from human urine and comparative study of two active forms of urokinase.

An improved method for the purification of high molecular weight urokinase to homogeneity from human urine was established. A yield of 32% with a 3,100-fold purification was obtained by Hyflo Super-Cel treatment, heat treatment at 60 degrees C for 10 hr, serial column chromatography on DEAE-Sepharose CL-6B and O-[3-(p-sulfophenylamino)-2-hydroxypropyl]-cellulose (SFOP-cellulose), and gel filtration on Ultrogel AcA 54. The low molecular weight form of urokinase was also purified to homogeneity by chromatography on hydroxyl apatite and gel filtration on Sephadex G-75 after the SFOP-cellulose column step. The high molecular weight urokinase had only one isoelectric form with a pI of 9.7, whereas the low molecular weight form had six isoelectric subforms with pI values between 9.4 and 6.4. The absorption coefficients at 280 nm of both urokinase forms were 13.61 and 13.50, respectively. Fibrinolytic and esterolytic activities of the two urokinase forms were compared in various assay methods.

Endopeptidases↗
PubMed1983

Threonine production by ethionine-resistant mutants of Serratia marcescens.

Ethionine reduced both the growth rate and the final growth level of Serratia marcescens Sr41. Growth inhibition was completely reversed by methionine. Strain D-315, defective in homoserine dehydrogenase I, was more sensitive to ethionine-mediated growth inhibition than was the wild-type strain. Ethionine-resistant mutants were isolated from cultures of strain D-316, which was derived from strain D-315 as a threonine deaminase-deficient mutant. Of 60 resistant colonies, 7 excreted threonine on minimal agar plates. One threonine-excreting strain, ETr17, was highly resistant to ethionine and, moreover, insensitive to methionine-mediated growth inhibition, whereas the parent strain was sensitive. When cultured in minimal medium with or without excess methionine, strain ETr17 had a higher homoserine dehydrogenase level than did strain D-316. The homoserine dehydrogenase activity was not inhibited by threonine or methionine. Transductional analysis revealed that the ethionine-resistant (etr-1) mutation carried by strain ETr17 was located in the metBM-argE region and caused the derepressed synthesis of homoserine dehydrogenase II. Strain ETr17 had a higher aspartokinase level than did the parent strain. By transductional cross with the argE+ marker, the etr-1 mutation was transferred into strain D-562 which was derived from D-505, a strain defective in aspartokinases I and III. The constructed strain had a higher aspartokinase level than did strain D-505 in medium with or without excess methionine, indicating that the etr-1 mutation led to the derepressed synthesis of aspartokinase II. Strain ETr17 produced about 8 mg of threonine per ml of medium containing sucrose and urea.

Chromosome Mapping↗
PubMed1983

Transductional construction of a threonine-hyperproducing strain of Serratia marcescens: lack of feedback controls of three aspartokinases and two homoserine dehydrogenases.

To construct a threonine-hyperproducing strain of Serratia marcescens Sr41, the six regulatory mutations for three aspartokinases and two homoserine dehydrogenases were combined in a single strain by three transductional crosses. The constructed strain, T-1026, carried the lysC1 mutation leading to lack of feedback inhibition and repression of aspartokinase III, the thrA1(1) mutation desensitizing aspartokinase I to feedback inhibition, the thrA2(1) mutation releasing feedback inhibition of homoserine dehydrogenase I, the two hnr mutations derepressing aspartokinase I and homoserine dehydrogenase I, and the etr-1 mutation derepressing aspartokinase II and homoserine dehydrogenase II. The strain produced ca. 40 mg of threonine per ml of medium containing sucrose and urea. Furthermore, the productivity of strain T-1026 was compared with those of strains devoid of more than one of the six regulatory mutations.

Alcohol Oxidoreductases↗
PubMed1983

l-Serine Production by a Mutant of Sarcina albida Defective in l-Serine Degradation.

For improved l-serine production, an l-serine dehydratase-defective mutant of Sarcina albida IAM 1012 was obtained. In the mutant, the activities of the enzymes responsible for l-serine production were as high as those in the parent strain, and, at a low glycine concentration, the mutant accumulated l-serine more efficiently than the parent. Under optimum conditions, 21 mg of l-serine per ml accumulated from 100 mg of glycine per ml. l-Serine was isolated from a reaction mixture as l-serine m-xylene-4-sulfonate, and free amino acid was obtained in high yields by use of an ion-exchange resin. Residual glycine was recovered at a yield of 61%.

Journal Article↗
PubMed1983

l-Tryptophan Production by Achromobacter liquidum.

Conditions for the production of tryptophanase from Achromobacter liquidum and for the conversion of l-serine and indole to l-tryptophan were studied. The enzyme could be produced in amounts as great as 0.750 U/ml (degradation) and 0.294 U/ml (synthesis) by shaking cultures at 30 degrees C in a medium containing dextrin, yeast extract, l-tryptophan, and l-glutamic acid. l-Tryptophan was produced most efficiently by shaking the cells at 37 degrees C in a reaction mixture containing 60 mg of l-serine per ml, 60 mg of indole per ml, and 0.5 mM pyridoxal phosphate. After 3 days, 96 mg of l-tryptophan per ml was formed, and l-tryptophan was easily isolated to 85.4% yield by concentration of the reaction mixture.

Journal Article↗
PubMed1981

Influence of Nutritional Conditions on Production of l-Glutamine by Flavobacterium rigense.

The nutritional conditions for the production of l-glutamine by Flavobacterium rigense strain 703 were investigated. The optimum concentration of ammonia for achieving the highest yield of l-glutamine (25 mg/ml of broth) was relatively broad, from 0.9 to 1.6%, whereas fumaric acid had a narrow optimum range, near 5.5%. High concentration of inorganic ions such as chloride or sulfate ion clearly inhibited cell growth. Therefore, ammonium salts other than (NH(4))(2)-fumarate were unsuitable for the highest production. The optimum concentration of (NH(4))(2)-fumarate was 7%. To reduce the concentration of fumaric acid in the medium, many substances were evaluated as substitutes. The fumaric acid concentration required for highest l-glutamine yield could not be replaced by any one of the compounds tested. However, part of fumaric acid could be replaced with succinic acid and cupric ion; 4% (NH(4))(2)-fumarate plus 2.5% succinic acid or 5% (NH(4))(2)-fumarate plus 1 mM cupric ion produced results similar to 7% (NH(4))(2)-fumarate in the fermentation medium.

Journal Article↗
PubMed1981

Mechanism of l-Glutamine Production by an l-Glutamine-Producing Mutant of Flavobacterium rigense.

Properties of some enzymes involved in l-glutamine biosynthesis in an l-glutamine-producing mutant of Flavobacterium rigense were examined. Glutamate-oxaloacetate transaminase in the mutant was nearly at the same level as that in the parent strain and was the most active among the enzymes participating in glutamate biosynthesis from alpha-ketoglutarate. Glutamine synthetase formation in the mutant was enhanced by increasing the concentration of (NH(4))(2)-fumarate in the medium, but the activity of this enzyme in the parent strain was very low, and its formation was not influenced by the concentration of (NH(4))(2)-fumarate. Glutaminase formation by both strains was similar and was not influenced by the levels of (NH(4))(2)-fumarate. Glutaminase activity of the mutant was inhibited by ammonia and fumarate. Intracellular amino acids and extracellular free amino acids in the mutant were compared with those of the parent strain. It seems reasonable to conclude that l-glutamine leaks out specifically through the cell membrane of strain 703 and that this specific excretion of l-glutamine probably allows a continuous conversion of l-glutamate to l-glutamine inside the cell.

Journal Article↗
PubMed1981

Production of l-Phenylalanine from trans-Cinnamic Acid with Rhodotorula glutinis Containing l-Phenylalanine Ammonia-Lyase Activity.

An enzymatic method using l-phenylalanine ammonia-lyase (EC 4.3.1.5) for the rapid conversion of trans-cinnamic acid to l-phenylalanine has been investigated. With Rhodotorula glutinis, enzyme activity as high as 0.3 U/ml of culture broth was obtained. The enzyme activity was kept stable for a relatively long time during cultivation by the addition of l-isoleucine. Optimization of the parameters of the conversion reaction resulted in accumulation of 18 mg of l-phenylalanine per ml of reaction mixture. The conversion yield from trans-cinnamic acid was about 70%. The method may provide a rapid and practical way to produce l-phenylalanine useful as an essential amino acid.

Journal Article↗
PubMed1981

beta-methylnorleucine, an antimetabolite produced by Serratia marcescens.

An amino acid was formed by alpha-aminobutyrate-resistant mutants of Serratia marcescens grown in a medium containing norvaline. This amino acid was identified as erythro-beta-methyl-L-norleucine [(2S,3S)-2-amino-3-methylhexanoic acid] by instrumental analyses. beta-Methylnorleucine inhibited the growth of several bacteria in synthetic medium.

Aminocaproates↗
PubMed1981

Biosynthetic pathway of beta-methylnorleucine, an antimetabolite produced by Serratia marcescens.

beta-Methylnorleucine biosynthesis was examined in Serratia marcescens using regulatory mutants of branched-chain amino acid biosynthesis. The accumulation of beta-methylnorleucine from norvaline in the wild-type strain was inhibited by the simultaneous additions of isoleucine, valine and leucine, although its accumulation in the derepressed mutant of isoleucine, valine and leucine biosynthesis was markedly increased and was not inhibited by additions of these amino acid. Accumulation of this compound was not observed in an isoleucine-valine auxotroph, although its accumulation was not affected in an isoleucine or leucine auxotroph. Transaminase B catalyzed the conversion of alpha-keto-beta-methylcaproate to beta-methylnorleucine. These results suggest that beta-methylnorleucine is formed from alpha-ketovalerate, alpha-ketoacid corresponding to norvaline, by enzymes of the isoleucine-valine biosynthetic pathway.

Anti-Bacterial Agents↗