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T Nagamune

Publications and source records attributed to T Nagamune.

46 records · Page 3Linked to original sources
PubMed1992

Light-induced oxidation of iron atoms in a photosensitive nitrile hydratase.

The photoactivation process of a photosensitive nitrile hydratase (NHase) from Rhodococcus sp. N-771 has been investigated by 57Fe Mössbauer spectroscopy and magnetic susceptibility measurements in order to clarify the behavior of iron atoms in the enzyme. Mössbauer spectra of inactive NHase gave two symmetric-doublet components indicating the presence of two iron species, while that of the active NHase gave a single symmetric doublet indicating the presence of a single iron species. Magnetic susceptibility measurements of the inactive and active HNase both showed small effective magnetic moments. These results led us to conclude that one of the two iron atoms incorporated in the NHase is oxidized during photoactivation, namely from a low spin ferrous to a low spin ferric state. This is the first observation of an intramolecular photooxidation phenomena involving iron in a single protein molecule.

Enzyme Activation↗
PubMed1992

Object-oriented fuzzy expert system for on-line diagnosing and control of bioprocesses.

An object-oriented fuzzy expert system to support on-line control of an automated fermentation plant is described. The major elements of the system consist of a fuzzy inference engine, a database, a knowledge base, and an expression evaluater. The expression evaluater calculates specific rates for growth, and substrate and product formation at different physiological states during the cultivation from the measured data. The specific rates are then compared with the standard target rates stored in the database. If differences outside the set tolerances were observed, the inference engine analyses the reasons for the faults on the basis of the knowledge represented in the form of a knowledge network and fuzzy membership functions of the process variables. The fuzzy expert system was developed on the basis of a shell constructed by using the object oriented Smalltalk/V Mac programming environment, with Lac-tobacillus casei lactic acid fermentation as the example of process application.

Biotechnology↗
PubMed1991

Crystallization of a photosensitive nitrile hydratase from Rhodococcus sp. N-771.

A photosensitive nitrile hydratase from Rhodococcus sp. N-771 has been crystallized in two different crystal forms in its inactive form. One crystal form belongs to an orthorhombic space group P2(1)2(1)2 with unit cell dimensions of a = 117.4 A, b = 145.7 A and c = 52.1 A, and the other form belongs to a hexagonal space group P6(3)22 with unit cell dimensions of a = 110.2 A and c = 412.1 A.

Crystallization↗
PubMed1990

Purification of inactivated photoresponsive nitrile hydratase.

Photoresponsive nitrile hydratase from Rhodococcus sp. N-771 was purified in its inactivated form. The enzyme had a molecular weight of approximately 60 kDa and consisted of 2 subunits each having molecular weight of 27.5 and 28 kDa. The enzyme also contained 2 iron atoms/enzyme as a cofactor. The enzyme was more stable in its inactivated form, rather than the activated during storage in the dark. The enzyme was most stable in the temperature region of 0-35 degrees C, and lost its activity above 40 degrees C. The enzyme was most stable in the pH region of 6-8. The optimum temperature and pH for the enzyme activity was 30 degrees C and 7.8, respectively. The enzyme showed wide substrate specificity, and most of the metal ions did not affect enzyme activity significantly. The absorption spectrum revealed the presence of some cofactor which changed form after photoirradiation.

Enzyme Activation↗
PubMed1990

A tubular bioreactor for high density cultivation of microorganisms.

By simulating the functions of the animal intestine, the authors have developed a novel tubular bioreactor (TBR) which is capable of containing both the reaction and separation of products in a single system. This reactor consisted of inorganic ultra filtration membrane modules in the primary part of the system, a heat exchanger and a recycling pump. The operation characteristics of the TBR were studied by cultivating Lactobacillus casei at a laboratory scale. The cell density obtained was up to 10 times higher than the density obtained by using the conventional jar fermentor. Furthermore, 40 g l-1 of cell mass was obtained in only 14 hours with 20 l of fresh medium when the dilution rate was increased according to the cellular growth. Afterwards, the cultivation time and the volume of fresh medium were reduced to 44% and 74%, respectively, of the values in the cultivation operation at constant dilution rate.

Bacteriological Techniques↗
PubMed1990

The inhibition by calmodulin of thyroid-stimulating hormone binding to epididymal fat, testis and thyroid membranes in the guinea-pig.

Calmodulin inhibited 125I-labelled TSH binding to the membranes of various target tissues for TSH (thyroid, epididymal fat and testis) of the guinea-pig. This inhibition was abolished by adding EGTA (1 mmol/l). Calmodulin did not inhibit the binding of 125I-labelled epidermal growth factor (EGF) to these membranes. It is suggested that the inhibitory effect of calmodulin on the binding of TSH to the receptor is specific and that this mechanism is due to the direct binding of calmodulin to receptor membranes. The ability of calmodulin to bind to the membranes was calcium-sensitive while that of TSH was not. The binding of 125I-labelled calmodulin to these membranes increased significantly when the endogenous calmodulin in the membranes was removed by EGTA. It was not inhibited by a pure preparation of TSH, but it was inhibited by contaminated calmodulin in a crude TSH preparation. On the other hand, 125I-labelled TSH binding to these membranes did not change after the removal of endogenous calmodulin. In conclusion, exogenous calmodulin has an inhibitory effect on the binding of TSH but not of EGF to the membranes of guinea-pig thyroid, epididymal fat and testis.

Animals↗
PubMed1990

Binding of bovine and porcine pituitary glycoprotein hormone alpha-subunit to TSH antibody in serum of patients with Graves' disease.

The characteristics of autoantibodies reactive with bovine (b) TSH were examined in the sera of six patients with Graves' disease selected on the basis of highly negative values in the TSH receptor assay. Test sera were incubated with other 125I-labeled pituitary glycoprotein hormones and their isolated subunits (alpha and beta) [human (h) TSH, bTSH, porcine (p) TSH, pFSH, bFSH, bLH and equine (e) chorionic gonadotropin (CG)] (purity was confirmed by gel-filtration on Sephadex G-100 and SDS-PAGE), and the antibody bound fraction was precipitated by the addition of anti-human gamma-globulin (goat). Almost all sera showed detectable binding to bTSH, pTSH, pFSH, pTSH-alpha, bFSH-alpha, bLH-alpha, but not to hTSH, hTSH-alpha, hTSH-beta, hFSH, hLH, hCG, pTSH-beta, bLH-beta, eCG-alpha. Exceptions were very low binding to bLH-beta by one serum and to pTSH-beta, by two sera. The level of binding (B/T%) of the patients' sera to pTSH-alpha, bFSH-alpha and bLH-alpha was 3.0-27.7%, 2.6-45.3% and 2.2-39.0%, respectively; that of sera from normal healthy adults was 1.9 +/- 0.3%, 0.8 +/- 0.2% and 0.9 +/- 0.2% (mean +/- SD), respectively. These results indicate that the TSH antibodies recognize mainly an epitope in the alpha subunit of bovine and porcine pituitary glycoprotein hormones (TSH, FSH, LH).

Animals↗
PubMed1989

Anti-TSH antibodies in Graves' disease and their failure to interact with TSH receptor antibodies.

The occasional occurrence in sera of patients with Graves' disease of negative values in the assay for TSH receptor antibodies led to the discovery of endogenous antibodies to TSH. We examined the sera of approximately 2500 patients with Graves' disease. Eight positive sera were found. The IgG in all 8 sera showed higher binding with both bTSH and porcine TSH (pTSH) than with human TSH (hTSH). This means that autoantibodies to TSH in sera from patients with Graves' disease are rare and often directed towards heterologous bovine and porcine TSH. When hTSH levels were determined in sera of hyperthyroid patients with positive antibodies to hTSH, discrepancies in serum hTSH levels were observed when using different assay methods, i.e. hTSH levels were higher with the double-antibody technique, and lower with immunoradiometric assays. Antibodies in these sera showed higher binding to pTSH-alpha subunit than to -beta subunit. The binding of the two pTSH subunits with antibodies could be displaced by intact bTSH. Neither stimulation in Graves' disease nor blocking in primary hypothyroidism of TSH receptor antibodies interfered with the binding of the anti-TSH antibodies to 125I-labelled pTSH, pTSH-alpha, and pTSH-beta. Consequently, using this type of autoantibodies to TSH we were unable to obtain evidence that the TSH receptor antibodies of patients with Graves' disease was an anti-idiotype antibody against anti-TSH antibodies.

Graves Disease↗