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

---

Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated adrenal cell preparation was used to investigate the relationship between ascorbic acid and steroidogenesis by two methods: (1) in vivo incorporation of exogenous [1-14C]ascorbic acid into endogenous ascorbic acid of adrenal by intraperitoneal injection of labeled ascorbic acid into rats and studying the depletion of labeled ascorbic acid under a variety of experimental conditions; and (2) study of the uptake of [14C]ascorbic acid by IAC in response to steroidogenic stimuli and various steroids. These studies demonstrate that: 1. IAC preparation by the trypsin digestion method results in almost total depletion of ascorbic acid from adrenal cells, i.e., ascorbic acid content of the cell preparation was less than 1% of the original ascorbic acid in quartered adrenal gland. 2. In spite of such a severe depletion of ascorbic acid, steroidogenesis in response to ACTH and dibutyryl cyclic AMP (dcAMP) is quite pronounced. 3. ACTH and dcAMP affect depletion of endogenously labeled ascorbic acid in IAC by a process that is both concentration- and time-dependent, but is independent of steroidogenic processes. 4. ACTH and dcAMP both inhibit the uptake of exogenous [1-14C]ascorbic acid, which is time-dependent but independent of the steroidogenic phenomenon. 5. The uptake of [14C]ascorbic acid by IAC is independent of extra-to-intracellular gradient of glucocorticoids or mineralocorticoids.
...
PMID:Effect of steroidogenesis on ascorbic acid content and uptake in isolated adrenal cells. 17 27

The rapid formation of adhesions in suspension by lightly trypsinized BHK21 cells is not dependent on protein synthesis, and only in part on cellular metabolism, although it is completely inhibited by heat- and aldehyde-fixation of the cells. A requirement for protein synthesis becomes evident only if cells are exposed to high levels of trypsin for long periods. Formation of adhesions does not require addition to the medium of divalent cations, although it is increased by divalent manganese and cobalt ions. It is promoted by cytochalasin B and by cyclic AMP and is not inhibited by p-mercuriphenylsulphonate. We discuss a possible relationship between aggregation and the formation of gap junctions.
...
PMID:Trypsinized BHK21 cells aggregate in the presence of metabolic inhibitors and in the absence of divalent cations. 17 27

Morphologically and functionally intact acinar cells have been obtained from the rat parotid gland through enzymatic dispersion with pure collagenase, hyaluronidase, and trypsin as well as mild mechanical forces. Cell yields of 30-50% of the original tissue weight with over 95% acinar cells were accomplished. The cells in suspension assumed a more or less spherical shape but the intracellular polarity of organelle distribution was maintained. The cells in suspension at 37 degrees C maintained stable monovalent cationic composition but lost potassium and gained sodium rapidly upon exposure to ouabain, 10(-5) M. The intracellular amylase concentration and the patterns of secretion of amylase and of synthesis of cyclic AMP by the cells in response to adrenergic stimulation with epinephrine or isoproterenol were comparable to those of the intact gland in situ. In addition, the cells showed good O2 consumption and maintained it constant for periods up to 8 h. These cells could be used as experimental tools for in vitro studies of receptor physiology and biochemistry, cell membrane function, cellular secretory mechanisms, and other parameters of exocrine gland cell physiology.
...
PMID:Dispersed rat parotid acinar cells. I. Morphological and functional characterization. 17 40

A manyfold increase in phosphorylation of cardiac sarcoplasmic reticulum (SR) was seen when SR was incubated in the presence of a bovine cardiac cyclic AMP-dependent protein kinase and cyclic AMP. This phosphoprotein had stability characteristics of a phosphoester in which the phosphate is incorporated largely into serine, and its formation did not required calcium ions, unlike the formation of acyl phosphoprotein intermediate of calcium-transport ATPase which is present within the same membrane. When examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the protein kinase-catalyzed phosphorylation occurred at a 22,000-dalton component of the cardiac sarcoplasmic reticulum. This 22,000-dalton protein has been named "phospholamban" (lambda alpha mu beta alpha nu epsilon iota nu = to receive), based on its ability to receive phosphate from ATP. Phosphorylation of phospholamban by cyclic AMP-dependent protein kinase was associated with the stimulation of calcium transport by the cardiac sarcoplasmic reticulum. This stimulation was accompanied by an increase in the calcium-activated ATPase activity, indicating that the overall rate of calcium transport rather than its efficiency is enhanced by protein kinase. The 22,000-dalton phopholamban was susceptible to trypsin. Brief digestion with trypsin in the presence of 1 M sucrose prevented subsequent phosphorylation of phospholamban, while leaving the calcium pump apparently intact. Incubation of trypsin-treated sarcoplasmic reticulum with cyclic AMP-depentent protein kinase did not result in the stimulation of calcium transport. These results may suggest that phospholamban is a modulator of the calcium pump of the cardiac sarcoplasmic reticulum.
...
PMID:Regulation of calcium transport in cardiac sarcoplasmic reticulum by cyclic AMP-dependent protein kinase. 17 97

Limited treatment of Escherichia coli DNA ligase with trypsin results in rapid loss of DNA joining activity. However, the ability to react with DPN to form the covalent enzyme-AMP intermediate is unaffected. The cleaved enzyme is also unable to catalyze the formation of DNA-adenylate, the second covalent intermediate in the ligase-catalyzed reaction. These findings demonstrate that portions of the DNA ligase molecule that are required for phosphodiester bond formation are not required for at least one of the partial reactions catalyzed by this enzyme.
...
PMID:Modification of Escherichia coli DNA ligase by cleavage with trypsin. 17 97

DSR stimulation in the supernatant fraction under the effect of 3', 5'-AMP 10(-7) M, ATP 5.10(-5) M, Mg2+5.10(-5) M, EDTA 5.10(-4) M and protamine 5 mg/ml was mediated through a factor which was readily sorbed by BaSO4, Al (OH)3 and activated carbon, and was easily eluated with a 10-fold increase of the buffer molarity. Barium eluates of the liver and of the brain restored the effect of 3', 5'-AMP eliminated by BaSO4, crosswise and equally. Apparently, the sorbed factor was a protein since it was not dialyzed, very thermolabile and readily inactivated by a low trypsin concentrations. The factor restored the DSR activation eliminated or decreased by the protein proteinkinase inhibitor (PPKI). A linear relationship between active quantities of the PPKI and the protein factor were in favour of the fact that the protein factor was affiliated or identical to proteinkinase. A possible biological significance of the DSR activation and the hypothesis on the existence of a special protamine-sensitive proteinkinase is discussed.
...
PMID:[Detection and study of a protein factor mediating stimulation of disulfide reductase activity by cyclic 3', 5'-AMP and other effectors]. 18 4

Bovine adrenocortical cells dispersed by trypsin digestion of fasciculata-reticularis minces were maintained in monolayer culture for up to 6 weeks. During the first week cells grown in medium containing ACTH (1 mU/ml) secreted steroids at a rate 10 to 20-fold greater than control cultures, cortisol accounting for 80-90% of the corticotrophic response. Using tracer amounts of [3H] progesterone and [3H] pregneolone, the major products were cortisol, corticosterone, 11-deoxycortisol and 11-deoxycorticosterone in decreasing order of magnitude. After 10 to 15 days in culture steroidogenesis was no longer enhanced by ACTH. This was concomitant with an apparent loss of 11 beta-hydroxylase activity which was mainly manifested by a sharp increase in the formation of 44-deoxycortisol. Short-term incubations of these cells during the first week in culture provided evidence that steroidogenesis was related to ACTH concentrations (from 0.1 to 100 muU/ml) and stimulated by dibutyryl cyclic AMP, the corticotrophic responses being further enhanced by theophylline (0.5to 50 mumoles/5 ml). Exposure of the cells to ACTH (50 muU/ml) resulted in a rapid increase in intracellular cyclic AMP contractions concomitant with a progressive increase in the corticosteroids released into the medium.
...
PMID:Preliminary observations of bovine adrenal fasciculata-reticularis cells in monolayer culture: steroidogenesis, effect of ACTH and cyclic AMP. 18 35

Trypsin increases intracellular levels of cylic AMP (cAMP) in lymphocytes. The trypsin-induced increase in cAMP is blocked by specific trypsin inhibitors and by high concentrations of different proteins. Several proteolytic enzymes from various sources, including other pancreatic proteases, do not cause an increase in cAMP under the same experimental conditions. Immobilized trypsin induced the same increase in cAMP as does free trypsin. The trypsin-induced rise in cAMP is not due to inhibition of cAMP phosphodiesterase, but consistent activation of adenylate cyclase by trypsin could not be demonstrated. The extent of the trypsin-induced increase in intracellular cAMP correlates with the type of the lymphocyte and with the state of maturity attained by the cells. Transformed lymphocytes and nonlymphoid cells do not react at all.
...
PMID:Trypsin-induced increase in intracellular cyclic AMP of lymphocytes. 18 38

In light of previous studies which have implicated prostaglandin (PG) formation as a link in ACTH-induced steroid production by isolated cat adrenocortical cells, experiments were carried out to provide additional information regarding the role of PGs in adrenal steroidogenesis and their interactions with calcium and cyclic AMP. Perfusion of cat adrenal glands with Locke's solution plus beta(1-24)-ACTH resulted in an immediate increase in PGF2alpha release, which rapidly declined to basal levels after the stimulus was withdrawn. In contrast, maximal rates of steroid release were manifest some 30 min after removal of ACTH. ACTH and its onitrophenyl sulfenyl derivative (NPS-ACTH) increased PG (PGF2alpha and PGE2) and steroid release by trypsin-dispersed cat cortical cells, but NPS-ACTH, unlike ACTH, did not augment cortical cyclic AMP levels. In this same preparation, indomethacin completely blocked ACTH and NPS-ACTH facilitated PGF2alpha and PGE2 release but failed to suppress steroid release markedly. Calcium-deprivation blocked PG and steroid release evoked by these two polypeptides, and depressed PG release elicited by monobutyryl cyclic AMP (bcAMP) without affecting steroid release. These experiments offer additional evidence to support the concept that PGs play a role in the mode of action of ACTH; however, they do not appear to be obligatory intermediates in the steroidogenic process. The importance of calcium in regulating PG formation is discussed with special regard for the idea that this cation has a direct action on the enzyme systems which control PG synthesis.
...
PMID:Further studies on the mechanisms controlling prostaglandin biosynthesis in the cat adrenal cortex: the role of calcium and cyclic AMP. 18 9

HMG CoA reductase, which catalyzes the reaction, HMG CoA + 2 NADAPH2 leads to mevalonate + CoA-SH + 2 NADP, is considered to be the rate-limiting enzyme on cholesterol biosynthetic pathway. Since a degree in activity of this enzyme is almost proportional to the rate of cholesterol synthesis from acetate, elucidation of factors that regulate reductase activity would provide insight into the control mechanisms on the cholesterol biosynthesis. In the present study, attempts were made to establish standard assay conditions of HMG CoA reductase activiy, and to qualify the factors affecting the activity of the enzyme. The results obtained were as follows: (1) As standard assay conditions of HMG CoA reductase activity, 85, muM were chosen for substrate concentration, 25-80 mug for microsomal enzyme protein, and 20 min for incubation time in a final volume of 0.1 ml. (2) HMG CoA reductase activity of rat liver microsomes was exhibited diurnal variation. The level of reductase activity at night was 4 fold higher than that of at daytime. (3) Either ATP or insulin administration stimulated hepatic HMG CoA reductase activity. But, cyclic AMP had no effect on reductase activity. The stimulatory effect of ATP or insulin on reductase activity was inhibited by a preadministration of glucagon. These results suggested that an interplay of hormone might regulate reductase activity and consequently cholesterol biosynthesis. (4) HMG CoA reductase activity was increased by preincubation of microsomes with cytosol. Presence of ATP or Mg++ intensified this effect. When digested by trypsin or degenerated by heat treatment, cytosol lost the stimulating activity. These results suggested as existence of protein factors in cytosol, which might modulate the enzyme interconversion from inactive to active forms.
...
PMID:[Studies on the regulatory factors of 3-hydroxy-3-methylglutaryl CoA reductase (HMG CoA reductase) activity]. 18 33


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---