Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thyroxine (T4), triiodothyronine (T3) and reverse triodothyronine (rT3) concentrations in human milk were measured by radioimmunoassay in 114 samples obtained from 1 week to 8 months postpartum. Several assay systems applied for the determination of serum thyroid hormone concentration were proved to be unsuitable for human milk, and the method of separating free and antibody-bound hormone by polyethylene glycol was also inappropriate for milk specimens, which tended to give a falsely high value. The binding of finity of T4 to milk was lower than that to serum protein, on which 8-anilino-1-naphthalene sulfonic acid showed no remarkable effect. In spite of the high sensitivity of 100 pg/tub in T4 assay system, no immunoassayable T4 was detected in all samples with or without ethanol extraction and trypsin hydrolysates of milk. In contrast, T3 was present in a measurable amount in most of the samples, the mean +/- SD value of which was 10 +/- 9 ng/100 ml, and those in colostrum were significantly higher than those in matured milk (P less than 0.01), whereas rT3 was not detectable in 76 samples tested. These results indicate that permeability of thyroid hormones through the mammary gland is different between T4 and T3 as well as in placental transport, and human milk can not be a source of thyroxine supply for the breast-fed infant.
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PMID:Presence of triiodothyronine, no detectable thyroxine and reverse triiodothyronine in human milk. 49 92

The ornithine decarboxylase-inducing factor (ODC factor) was purified about 1,000-fold in 42% yield from the ascites fluids of an Ehrlich ascites tumor by a combination of centrifugation and concanavalin A (ConA) treatment. A single ip injection of 0.5 micrograms of the purified factor per mouse resulted in half-maximum induction of liver ODC. The factor was found to be a trypsin- and chymotrypsin-resistant, acidic glycoprotein (pI about 4.43) with a minimum molecular weight of about 70 kilodaltons, containing a disulfide bond(s) in its functional domain. It did not react with ConA. This factor induced retrodifferentiation of liver function, causing a marked increase of prototype M2 isozyme of pyruvate kinase. It reduced liver catalase activity, and also modified thyroid hormone metabolism, reducing the serum levels of T4 and T3. These results suggest that the ODC factor is multifunctional and induces many of the changes observed in a tumor-bearing host.
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PMID:Purification of ornithine decarboxylase-inducing factor from cell-free ascites fluid of Ehrlich ascites tumor and its characteristics. 170 56

Comparative and competitive analyses of thyroxine (T4) and triiodothyronine (T3) binding to highly purified rat liver, brain and lung cell plasma membranes were carried out. The dependence of hormone binding on the time, temperature and concentration was studied. The effects of trypsin and partial delipidation on the binding parameters of thyroid hormones were investigated. Two thyroid hormone-binding sites were detected in cell plasma membranes of all tissues under study. The maximal binding of T4 to rat liver membranes and the maximal binding of T3 to rat brain membranes was observed in all experiments, the affinity for T3 being higher than that for T4. An important role of both protein and lipid components of plasma membranes in the membrane reception of thyroid hormones is proposed.
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PMID:[Membrane reception of thyroid hormones]. 174 13

Recent studies from this laboratory have demonstrated the presence of thyroid hormone response elements (TREs) in the 5'-flanking region of the rat alpha and TSH beta subunit genes. Using an avidin-biotin complex DNA binding assay, we have shown that these TREs bind the thyroid hormone (T3) receptor present in nuclear extracts of GH3 cells, as well as the in vitro synthesized Hc-erbA beta, which has been identified as a member of the family of T3 receptors. The binding of Hc-erbA beta to the alpha subunit TRE can be enhanced 3-4-fold by including GH3 nuclear extract in the binding assay. Binding to the TRE present in the TSH beta gene or the rat growth hormone gene was similarly enhanced, although to a lesser degree. The enhanced binding activity is trypsin-sensitive and heat labile, and is not reproduced by the addition of histones, bovine serum albumin, or cytosol instead of nuclear extract. Gel exclusion chromatography suggests a molecular size of approximately 65,000 Da. This protein, which is present in several different cell types, is also able to complement binding of the rat erbA alpha-1 and the pituitary-specific erbA beta-2 forms of the receptor. These data suggest that the binding of the T3 receptor to a TRE is augmented by another nuclear protein, which may be involved in the mechanism of action of thyroid hormone.
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PMID:A nuclear factor that enhances binding of thyroid hormone receptors to thyroid hormone response elements. 196 58

Hepatic nuclear thyroid hormone receptors from rat, dog, chicken, and rainbow trout were compared. Receptor affinities for 3,5,3'-triiodo-L-thyronine (T3) were similar in preparations from rat, dog, and chicken, using isolated nuclei and nuclear extracts. Rainbow trout nuclear receptor showed a lower affinity for T3. Almost half of the receptors were released into the medium with rat and chicken nuclei, and 79.7 +/- 1.1% of the receptors were released with rainbow trout nuclei, when isolated nuclei were incubated with T3 at 22 degrees for 2 hr. The affinity constant of rat liver receptor for calf thymus DNA-cellulose at 0.17 M KCl, pH 7.4, was 3.98 +/- 1.47 x 10(5) M-1, when determined using DNA-cellulose columns. The number of salt bridges involved in DNA binding of the rat receptor was 5.73 +/- 0.38. When receptor-DNA interactions were compared among species, significant differences were found, but the receptors from dog and rainbow trout liver were similar. Sephacryl S-200 column chromatography showed that chicken receptor had a Stokes radius significantly smaller than that of rat receptor. Partial proteolysis of T3-receptor complex using trypsin alpha-chymotrypsin, elastase, and papain produced distinct T3-binding fragments in different species. Our data provide evidence that nuclear thyroid hormone receptors from different species have significant structural dissimilarities.
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PMID:Differences in nuclear thyroid hormone receptors among species. 250 Mar 75

The placenta may be involved in the regulation of the maternal thyroid function during pregnancy. As human chorionic gonadotropin (hCG) is a primary protein from the placenta, we examined the thyrotropic activity of hCG and its derivatives using tissue culture and monolayer cell culture of human thyroid glands. The TSH receptor preparation was made from thyroid tissues, and its binding affinity with hCG and Asialo hCG (As-hCG) was examined. hCG did not bind to TSH receptor, but As-hCG did. In the experiment with tissue culture, TSH, hCG, hCG alpha, beta subunit and As-hCG were added to the culture medium. Secretions of L-thyroxine (T4) and L-triiodothyronine (T3) in the culture medium were measured at regular time intervals. While TSH showed increases of T4 and T3 secretion, other hCG derivatives did not show any differences from the control values. When TSH and hCG were added together, the secretion of thyroid hormone was the same as that obtained by TSH single administration. On the other hand, the secretion of T4 and T3 was inhibited with co-administration of TSH and As-hCG. Only TSH and none of the other hCG derivatives showed the dose-dependent stimulation of T4 and T3 secretion. A similar experiment was carried out in a monolayer cell culture obtained by trypsin treatment of human thyroid tissue. The secretions of cyclic AMP (c-AMP), T4 and T3 were measured. As in the previous tissue experiment, the thyrotropic activity of TSH was not modified by hCG, but the secretions of T4, T3 and especially c-AMP were inhibited by co-administration of As-hCG and TSH. These findings suggest that hCG and its subunits do not show thyrotropic activity in human thyroid glands, but As-hCG acts as an antagonist of TSH.
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PMID:[Studies on the thyrotropic activity of hCG and its derivatives]. 300 61

Explants of tadpole tail skin secreted a factor which induces the thyroid hormone-dependent regression of the tail mesenchyme. The activity of the factor was not sensitive to digestion with trypsin or pronase. Heating at 120 degrees C but not at 100 degrees C for 20 min destroyed the activity. The factor came out gradually through a dialysis membrane. The factor was retarded on a Sephadex G-10 column and eluted with water after the salts fraction. We suggest that the active principle is a non-proteinaceous substance with a low molecular weight.
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PMID:An epidermal factor which induces thyroid hormone-dependent regression of mesenchymal tissues of the tadpole tail. 349 Apr 13

The coupling of iodotyrosine (coupling reaction) is one of the least studied in the formation of thyroid hormone, particularly in human thyroid diseases. This paper describes a method of measuring iodotyrosine coupling catalyzed by human thyroid peroxidase (TPO) in vitro. There were two important requirements to demonstrate the coupling reaction: 1) thyroglobulin with a low thyroid hormone content, and 2) partially purified TPO. Thyroglobulin with low thyroid hormone content was obtained from Grave's and follicular adenoma tissues after propylthiouracil (PTU) therapy and L-T4 therapy, respectively. TPO was prepared from Graves' thyroid by solubilizing the 100,000 X g pellet of thyroid homogenate with sodium deoxycholate and trypsin, followed by Sephacryl S-300 gel filtration. Before the coupling reaction, thyroglobulin was iodinated with chloramine-T and potassium iodide, followed by dialysis. The coupling reaction was carried out by incubating newly iodinated thyroglobulin with TPO, diiodotyrosine, a coupling stimulator, and a H2O2-generating system (glucose and glucose oxidase) for 20 min at 37 C. After thyroglobulin was digested with Pronase, the thyroid hormone content of the thyroid digest was measured by RIA. Coupling activity was measured by the amount of newly formed T3 (nanograms of T3 per mg thyroglobulin). The time course of coupling reaction showed a progressive increase in coupling activity up to 30 min, and the reaction was temperature and pH dependent, with a pH optimum of 7.0. Coupling activity in the presence of H2O2 and TPO was 43 +/- 5.0 ng T3/mg thyroglobulin (mean +/- SD of triplicate samples), and addition of diiodotyrosine to the H2O2-TPO system caused a nearly 3-fold increase in coupling activity. This method has potential utilization for measurement of peroxidase coupling activity, since there was a linear relationship between the measured coupling activity and the amount of added TPO when the TPO concentration was over 3 micrograms/300 microliter. Methimazole (MMI) and PTU had similar potencies in inhibiting the TPO-catalyzed coupling reaction, whereas MMI was distinctly more potent than PTU as an inhibitor of TPO-mediated iodination in vitro. The different potencies of MMI in the two reactions suggest that different inhibitory mechanisms may be involved in iodination and coupling. The reducing agent, sodium metabisulfite, was also found to be a more potent inhibitor of the TPO-mediated coupling reaction than of the TPO-mediated iodination reaction. The method of iodotyrosine coupling described here may be useful to investigate the coupling step of thyroid hormone formation in human thyroid diseases.
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PMID:Coupling of iodotyrosine catalyzed by human thyroid peroxidase in vitro. 383 97

The effect of thyroid hormone on the generation of modulators of mitochondrial protein synthesis was investigated. The modulators were present in the 150,000 X g supernatant (S-150) prepared from Wistar rat liver and kidney. In young rats (50 g BW), a stimulator was found in liver, and an inhibitory modulator was present in kidney tissue. Generation of these modulators was stimulated by T4 administration to the animals. In aged rats (200 g BW), the production of an inhibitory modulator in both liver and kidney was stimulated by thyroid hormone administration. Both the stimulatory and inhibitory modulators were inactivated by pretreatment with trypsin. The mol wt of these modulators was estimated by gel filtration study, and for both the stimulatory and inhibitory modulator proteins was approximately 10,000. The results suggested that thyroid hormone regulates mitochondrial protein synthesis through the stimulation of synthesis of mitochondrial protein synthesis modulators and that the tissue-specific modulators (stimulatory in liver and inhibitory in kidney) can be produced in young animals. In aged animals, however, it is postulated that thyroid hormone stimulates biosynthesis of an inhibitory modulator in both liver and kidney.
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PMID:Evidence for induction by thyroid hormone of cytosolic proteins which control mitochondrial protein synthesis. 404 62

The effect of thyroid hormone on the generation of modulators of mitochondrial protein synthesis was investigated. The modulators were present in the 150,000 X g supernatant (S-150) prepared from Wistar rat liver and kidney. A stimulator was found in the liver, and an inhibitory modulator was present in kidney tissue. Generation of these modulators was stimulated by T4 administration to the animals. Both the stimulatory and inhibitory modulators were inactivated by pretreatment with trypsin or boiling. The molecular weight of these modulators was estimated by gel filtration study and for both the stimulatory and inhibitory modulator proteins was approximately 10,000 daltons. The results suggested that thyroid hormone regulates mitochondrial protein synthesis through the stimulation of synthesis of mitochondrial protein synthesis modulators, and that the tissue specific modulators (stimulatory in liver and inhibitory in kidney) can be produced by the hormone.
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PMID:[Induction of cytosolic proteins controlling mitochondrial protein synthesis by thyroid hormone]. 409 84


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