Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

A membrane fraction enriched in parathyroid hormone (PTH)-sensitive adenylate cyclase and sodium and potassium ion-activated (Na+, K+)-ATPase was prepared from bovine kidney. Tritiated PTH binding to this membrane fraction was dependent on both hormone and membrane protein concentration. Both total and specific binding of the hormone decreased significantly after 5 to 10 min of incubation at 22 degrees. PTH binding was highly specific, being sensitive to inhibition only with active forms of unlabeled hormone (native and 1-34 PTH). Specific binding showed a pH optimum of 7.3 to 7.5. Inhibition of binding of tritiated hormone by unlabeled PTH was also highly effective at pH 6.0, but this apparently specific binding was also inhibited by adrenocorticotropic hormone, insulin, glucagon, and vasopressin. Dissociation of bound hormone was demonstrated, and an apparent dissociation constant of 4.6 X 10(-2) min-1 was obtained. Specific binding was eliminated by pretreatment of the membranes with trypsin. The concentration dependence for inhibition of binding with unlabeled PTH was identical to that for activation of adenylate cyclase in this membrane preparation, and binding was also inhibited by concentrations of calcium in the 0.5 to 2 mM range.
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PMID:Binding of tritiated bovine parathyroid hormone to plasma membranes from bovine kidney cortex. 1 29

Rat adrenal cortical cells have been prepared by collagenase dissociation of trypsin-treated adrenal tissue. The content and compositions of cholesteryl ester, phospholipid, and triglyceride fatty acids compare favorably with those of undissociated rat adrenal tissue. During 2-hour control incubations of adrenal cortical cells, steroidogenesis was not detected, and the levels of sterol ester, phospholipid, and triglyceride fatty acids were not significantly altered. Incubations with adrenocorticotropic hormone (ACTH) resulted in coricosterone production and significant depletions of sterol ester and triglyceride fatty acids, but not of phospholipid fatty acids. Although all fatty acid esters of cholesterol were hydrolyzed under these conditions, the greatest contributions to the net decrease in sterol esters were by oleate, arachidonate, and adrenate. Incubations with dibutyryl cyclic adenosine monophosphate (0.5 mM) resulted in significantly greater levels of corticosterone production than did ACTH (250 muunits), but the effects on cellular lipids were comparable to those seen with the tropic hormone. This study represents the first demonstration of hormone-induced hydrolysis of sterol esters in an in vitro cell suspension system. The results are discussed with respect to hormone-sensitive sterol ester hydrolase of adrenal cortex, and to the role of endogenous cholesteryl esters in the steroidogenic pathway.
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PMID:ACTH-induced hydrolysis of cholesteryl esters in rat adrenal cells. 20 12

The high molecular weight forms of adrenocorticotropic hormone (ACTH) produced by mouse pituitary tumor cells (AtT-20/D-16v) were separated from each other by gel filtration; their ability to stimulate steroidogenesis by isolated rat adrenal cortical cells was studied. Pools of pro-ACTH/endorphin. ACTH biosynthetic intermediate, and glycosylated ACTH(1--39) were obtained; on the basis of NaDodSO4-polyacrylamide gel electrophoresis, over 97% of the immunoactive ACTH was found to have the expected molecular weight. Suspension of isolated rat adrenal cortical cells were incubated overnight in tissue culture medium and used in a 2-h steroid production assay. Synthetic human ACTH(1--39) [hACTH(1--39)] was used as a bioassay and immunoassay standard; 60 pM hACTH(1--39) stimulated half-maximal production of fluoregenic steroid. The amount of pro-ACTH/endorphin, ACTH biosynthetic intermediate, or glycosylated (ACTH(1--39) added was estimated with an ACTH(17--24) immunoassay. All three high molecular weight forms of ACTH are capable of stimulating the same maximal level of steroidogenesis as hACTH(1--39). Glycosylated ACTH(1--39) is equipotent with hACTH(1--39); ACTH biosynthetic intermediate and pro-ACTH/endorphin are, respectively, 100- and 300-fold less potent than hACTH(1--39). Steroid production in response to all four forms of ACTH is linear in time. All of the different forms of ACTH stimulate the synthesis of corticosterone and related steroids; no significant production of cortisol or aldosterone was observed. beta-Lipotropin (beta LPH) and 16K fragment, which comprise the non-ACTH regions of pro-ACTH/endorphin and are secreted by the pituitary tumor cells, did not stimulate or interfere with steroidogenesis. Brief incubations of pro-ACTH/endorphin and ACTH biosynthetic intermediate with trypsin generated lower molecular weight forms of ACTH and increased biological activity 50-fold; thus, the decreased steroidogenic potency of these forms of ACTH is thought to be due to structural constraints on the ACTH(1--39)-like sequence in these larger precursor molecules
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PMID:Steroidogenic activity of high molecular weight forms of corticotropin. 22 22

The hypothesis that the COOH-terminal heptapeptide mediates the aldosterone-stimulating activity of angiotensin II was evaluated by comparing the relative effects on aldosterone production of angiotensin II and the heptapeptide to angiotensin analogues that are poorly metabolized to the heptapeptide and to a nonapeptide, des-Asp-1-angiotensin I, that is directly converted to the heptapeptide. In in vivo studies utilizing the adrenocorticotropic hormone-suppressed bilaterally nephrectomized dog, angiotensin II and the heptapeptide produced statistically significant increases in both aldosterone and cortisol secretory rates (P less than 0.001 for both relations). Sar-1-angiotensin II stimulated the production of both steroids to the same extent, but had much longer duration of action. [Poly(oAc)Seryl]angiotensin II was a weak agonist, having only about 30% of the steroidogenic potency of either angiotensin II or the heptapeptide. In equimolar concentrations des-Asp-1-angiotensin I had about one-half of the aldosterone-stimulating activity of the hepatpeptide. In in vitro studies, employing the trypsin-dispersed cat adrenal zona glomerulosa cells, the steroidogenic potency of angiotensin II and the heptapeptide was identical to maximal aldosterone production of 10(-8) M peptide concentration. By contrast, the response to Sar-1-angiotensin II was approximately a 10-fold increase in relative potency, while the response to [poly(oAc)Seryl]angiotensin II demonstrated a 10-fold decrease. These findings suggest that, although the heptapeptide may play an important role in the regulation of aldosterone production, the possibility remains open that angiotensin II could stimulate aldosterone biosynthesis without prior conversion to the heptapeptide.
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PMID:The role of angiotensins in aldosterone production. 126 9

The effects of adrenocorticotropic hormone (ACTH), human chorionic gonadotropin (hCG) and prostaglandin E2 (PGE2) on the progesterone secretion of luteal cells from rats were studied. Corpora lutea were harvested on Day 6 of pseudopregnancy and digested by trypsin. Homogeneous suspensions of luteal cells were used for short-term incubation. ACTH, PGE2, and hCG were added to the medium and the changes in progesterone production were measured by radioimmunoassay (RIA). Furthermore, specific ACTH-binding sites of the luteal cell membrane were studied by Scatchard analysis. ACTH, PGE2 and hCG increased synthesis of progesterone, and the combination of hCG with ACTH or PGE2 further increased production of the hormone. The effect of ACTH could be prevented by indomethacin. These effect of ACTH seem to be connected with specific ACTH-binding sites of the luteal cell membrane and with increased production of PGE2.
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PMID:Stimulation of progesterone production by adrenocorticotropic hormone and prostaglandin E2 in rat luteal cells. 301 65

Parathyroid hormone is mainly regulated by the serum calcium concentration and not by another hormone which is usually the case for other hormones. We examined whether the parathyroid hormone could also be regulated by a hormone such as adrenocorticotropic hormone (ACTH). Experiment I: A two-hour urine sample was collected from 6 AM to 8 AM. At 8 AM one mg of synthetic ACTH was injected intramuscularly. Blood and urine was collected two hours after the injection for determination of the concentration of serum calcium, phosphate, parathyroid hormone and cortisol. Experiment II: Adenoma tissue was obtained during operation from patients with primary hyperparathyroidism. The adenoma was digested with trypsin. Eagle MEM containing 100 ml fetal calf serum per 500 ml medium was used as the culture medium. The specimens were incubated in an atmosphere of 95% air and 5% CO2. Several days later, 25 micrograms of ACTH was added to the medium which was then incubated for 2 hours. The parathyroid hormone in the medium was measured by radioimmunoassay. Experiment III:ACTH was injected intraperitoneally into control male rats and parathyroidectomized rats. Two hours later, serum calcium and parathyroid hormone levels were measured. After ACTH injection, a remarkable increase in serum calcium level was seen in the patients with primary hyperparathyroidism, but in the other groups, no increase in the serum calcium was observed. Parathyroid hormone was increased after ACTH injection in most subjects in all groups. Serum cortisol levels increased markedly after ACTH injection in all groups. The parathyroid concentration in the culture medium was slightly increased after ACTH addition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Endocrinological characteristic of primary hyperparathyroidism]. 609 27

Many small biologicaly active peptides are derived from larger precursor forms which fulfil a variety of roles in the synthesis, segregation and intracellular migration of secretory products. Limited proteolysis may occur at several stages during this process, giving rise to products that are either degraded (e.g. the prepeptides) or discharged coordinately from their cells of origin during exocytosis (e.g. insulin and C-peptide). Molecular defects have recently been found to occur at cleavage sites in proinsulin as well as in other proproteins, and these point mutations may, in some instances, be responsible for familial metabolic disorders. The nature and cell specificity of the proteolytic enzymes involved in the conversion of the various precursor forms remains unresolved. Recent studies in our laboratory have led to the identification of precursors of glucagon and somatostatin in rat islets of Langerhans. Analysis of tryptic maps of these precursors has shown that a trypsin-like enzyme would be sufficient to cleave the C-terminally located somatostatin sequence from its precursor (relative molecular mass 12,500), but that both trypsin-like and carboxypeptidase B-like enzymes would be necessary to cleave the internal glucagon sequence from its prohormone (relative molecular mass 18,000). Molecular cloning techniques have provided valuable new approaches to analysing the structures of a variety of precursor forms, including those for insulin, gastrin, growth hormone, adrenocorticotropic hormone and the endorphins, and in the future will undoubtedly shed more light on the structures of their chromosomal genes, the mechanisms regulating their expression, and their evolutionary origins.
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PMID:Formation of biologically active peptides. 610 30

Crude extracts of rat atria reduced the basal amount of aldosterone released from rat zona glomerulosa cells and partially inhibited aldosterone stimulation by adrenocorticotropic hormone and angiotensin II. The destruction of this activity by trypsin suggests that the active factor is a peptide, possibly atrial natriuretic factor. These data suggest that atrial natriuretic factor affects sodium excretion by the kidneys both directly and through the inhibition of aldosterone production.
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PMID:Inhibition of aldosterone production by an atrial extract. 632 67

Receptor sites for insulin on GH3 cells were characterized. Uptake of 125I-labeled insulin by the cells was dependent upon time and temperature, with apparent steady-states reached by 120, 20 and 10 min at 4, 23 and 37 degrees C, respectively. The binding sites were sensitive to trypsin, suggesting that the receptors contain protein. Insulin competed with 125I-labeled insulin for binding sites, with half-maximal competition observed at 5 nM insulin. Neither adrenocorticotropic hormone nor growth hormone competed for 125I-labeled insulin binding sites. 125I-labeled insulin binding was reversible, and saturable with respect to hormone concentration. 125I-labeled insulin was degraded at both 4 and 37 degrees C by GH3 cells, but not by medium conditioned by these cells. After a 5 min incubation at 37 degrees C, products of 125I-labeled insulin degradation could be recovered from the cells but were not detected extracellularly. Extending the time of incubation resulted in the recovery of fragments of 125I-labeled insulin from both cells and the medium. Native insulin inhibited most of the degradation of 125I-labeled insulin suggesting that degradation resulted, in part, from a saturable process. At steady-state, degradation products of 125I-labeled insulin, as well as intact hormone, were recovered from GH3 cells. After 30 min incubation at 37 degrees C, 80% of the cell-bound radioactivity was not extractable from GH3, cells with acetic acid.
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PMID:Binding and degradation of 125I-labeled insulin by a clonal line of rat pituitary tumor cells. 634 60

The possible role of cortisol in development of the exocrine pancreas was investigated. In the first study, fetal pigs were removed from the uterus by caesarean section (pentobarbitone anesthesia) and the pancreas collected from 51 69 to 109-day-old fetuses (term = 114 +/- 2 days). Of these, 15 88 to 90-day-old fetuses had been infused subcutaneously for 6 days with either saline, adrenocorticotropic hormone or cortisol (osmotic mini-pumps implanted at 82-84 days). The pancreas was also removed from eight newborn pigs. Quantitative enzyme analysis showed that amylase and trypsin activities per milligram pancreatic protein increased toward term, correlated positively with fetal plasma cortisol (p < 0.01) and were stimulated by cortisol infusion (p < 0.05). In the second study, pigs were delivered by caesarean section 2-3 days before term (to circumvent the neonatal cortisol surge) and injected intramuscularly with saline (n = 11), metyrapone (an inhibitor of cortisol synthesis, n = 12), adrenocorticotropic hormone (n = 14) or cortisol acetate (n = 6) during the postnatal period. At 6-7 days of age, adrenocorticotropic hormone- and cortisol acetate-treated pigs had higher concentrations of amylase and trypsin in pancreas than metyrapone-treated pigs. The values in saline-injected pigs were intermediate. By gel electrophoresis and subsequent incubation with enzyme substrates, protease E, chymotrypsin C, and cathodic trypsin were first detected at 6-7 days of age, and the activities (semiquantitative densitometry) appeared lower in metyrapone-treated pigs than in pigs from other treatment groups. The results indicate that glucocorticoids stimulate the perinatal development of pancreatic enzymes in the pig.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Developmental regulation of the porcine exocrine pancreas by glucocorticoids. 752 4


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