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)

Big renin has a greater molecular weight (63,000 versus 43,000) than normal renin, but it shares the characteristic enzymatic and immunologic properties of normal renin. As it exists in the kidney or plasma of a patient, big renin is less active than normal renin, but its enzymatic activity is greatly enhanced by exposure to pH values of 3.0 to 3.6 or by brief incubation with pepsin or trypsin. Use of the terms prorenin and zymogen might be withheld until big renin is shown to exist in normal tissue or plasma and to be converted to normal renin in vivo. To date, big renin has been found in renal tumors and other abnormal kidney tissues as well as in the plasma of patients with renal disorders. The remarkable activation of big renin at pH levels of 3.3 can be used to detect its presence. If a method involving acidification is used to quantitate plasma renin activity of a patient with circulating big renin, the activated plasma renin activity greatly exceeds that measured in plasma maintained at neutral pH. Gel filtration of plasma is used to prove the presence of big renin. When large amounts of big renin are secreted by a renal tumor, hyperfusion may ensue and be cured by removal of the tumor. The secretion of small amounts of big renin does not necessarily result in any physiologic disorder. However, if there is a concomitant diminution or absence of normal renin a state of apparent hyporeninemia exists, as we have observed in diabetic nephropathy; this may be associated with hypoaldosteronism and hyperkalemia. Big renin does not appear to respond to physiologic changes that stimulate or suppress normal plasma renin activity. The finding of big renin may indicate the presence of certain renin-secreting renal tumors or other renal disorders, especially diabetic nephropathy.
Am J Cardiol 1976 Mar 31
PMID:Big renin: identification, chemical properties and clinical implications. 125 3

Junctional SR membrane vesicles have been isolated from chronically failing human hearts explanted at transplant operations. Vesicles have been incorporated into artificial planar phospholipid bilayers and the activity of single calcium-release channels investigated under voltage-clamp conditions. The properties of these channels are similar to those previously reported from normal animal tissue and do not provide evidence that the function of individual calcium-release channels is altered in the failing heart. Using radio-labelled ryanodine binding as a specific marker for the calcium-release channel, we demonstrate that, in the sheep heart, ischaemia results in the degradation of the calcium-release channel. The activation of proteases and oxidant stress in the ischaemic and re-perfused post-ischaemic myocardium are likely mediators of cell injury. Using the protease trypsin and the photosensitisation of rose bengal to generate the reactive oxygen species (ROS) singlet oxygen and superoxide radicals we demonstrate a direct effect on the calcium-release channel in vitro. Exposure of junctional SR vesicles to trypsin or oxidant stress resulted in the progressive loss of specific ryanodine binding and the degradation of high molecular weight proteins identified by polyacrylamide gel electrophoresis. The activity of single channels was also modified during exposure to proteolysis or oxidant stress; an initial increase in channel opening was observed followed by irreversible loss of channel function. Degradation of specific proteins, such as the calcium-release channel, may contribute to contractile dysfunction in the ischaemic and reperfused post-ischaemic myocardium.
Basic Res Cardiol 1992
PMID:The calcium-release channel from cardiac sarcoplasmic reticulum: function in the failing and acutely ischaemic heart. 132 62

The adult newt cardiac ventricular myocyte has been successfully placed in cell culture and has been shown to undergo in vitro DNA synthesis. Although several growth factors have been reported to increase DNA synthesis in cardiac myocytes in vitro, PDGF has not been reported to do so, but has been shown to be active in other systems. Ventricles were removed from the adult red-spotted newt and were enzymatically and mechanically dissociated in a solution containing trypsin and collagenase. Cells were preplated on to plastic to remove non-myocytes. Myocytes were then plated onto laminin. Groups of myocytes were fed control medium and medium containing porcine PDGF. Myocytes were given 1 microCi/ml of tritiated thymidine 6 or 24 h before fixation. Control myocytes showed a peak DNA synthesis at 12-14 days in culture. One ng/ml of PDGF increased DNA synthesis significantly to 22% above control. Myocytes responded to PDGF with significantly increased DNA synthesis in about 12 h. PDGF did not induce earlier DNA synthesis, but increased synthesis at all days of culture tested. These results indicate that PDGF acts upon cardiac myocytes, increasing their DNA synthesis.
J Mol Cell Cardiol 1992 Sep
PMID:Stimulation of DNA synthesis by PDGF in the newt cardiac myocyte. 143 20

Fast inactivation of Na channels in neonatal cardiac cells was removed by the action of proteolytic enzymes trypsin or papain. Two stages were apparent in the time course of this process. During the first one, both number of channel reopenings and the mean open time increased markedly even though fast inactivation remained complete. The second stage was manifested by the disappearance of all signs of fast inactivation without further noticeable changes in channel mean open time. At the same time the nonrandom clustering of blank response (response without channel openings) trials became prominent. The data obtained support the interpretation of two separate fast inactivation states in cardiac Na channels as suggested in our previous papers (Zilberter et al. (1989) in Neuromuscular Junction (Sellin, L.C., Libelius, R. and Thesleff, S., eds.), pp. 43-50, Elsevier, Amsterdam, and Zilberter et al. (1991) J. Mol. Cell. Cardiol. 23, (Suppl.) 61-72).
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PMID:Existence of two fast inactivation states in cardiac Na channels confirmed by two-stage action of proteolytic enzymes. 165 6

Three to six mg of the millimolar Ca2+-requiring proteinase (m-calpain) were obtained from 1 kg bovine cardiac muscle (fresh wt) and some enzymatic properties of this proteinase were determined. Activity of bovine cardiac m-calpain decreases as ionic strength increases from 75 to 1000 mM. Maximal activation of m-calpain by Ca2+, La3+, Ba2+, and Mn2+ occurs at 2 to 3 mM concentrations of each of these divalent cations, but La3+ activation is only 20 to 25% and Ba2+ and Mn2+ activation only 6 to 10% as great as Ca2+ activation. Maximum Sr2+ activation occurs at 20 mM Sr2+ and is 90 to 95% of maximum Ca2+ activation. Mg2+, Zn2+, Cr2+, and Cd2+ do not activate m-calpain when added alone; Mg2+ does not affect, but Zn2+ inhibits, Ca2+-stimulated activity. The nonionic detergents, Triton X-100 and Brij 35, activate m-calpain 1.6- to 2.0-fold but do not change its Ca2+ requirement. Sodium dodecyl sulfate and urea inhibit m-calpain completely at 0.045% and 2.0 M, respectively. Because they bind Ca2+ needed for activation, ATP, ADP, and ITP inhibit m-calpain. The trypsin inhibitors, phenylmethylsulfonyl fluoride, ovomucoid trypsin inhibitor, ovoinhibitor, aprotinin, alpha 1-antiproteinase inhibitor, soybean trypsin inhibitor, and lima bean trypsin inhibitor do not affect m-calpain activity; m-calpain does not release measureable quantities of acid-soluble peptides from a rabbit skeletal sarcoplasmic protein fraction but does degrade rabbit skeletal myofibrils and casein.
J Mol Cell Cardiol 1988 Nov
PMID:Some properties of the millimolar Ca2+-dependent proteinase from bovine cardiac muscle. 285 32

Cardiac rat myocytes in primary culture exhibit a membrane-bound and a secreted form of plasminogen activator (PA). Growth of the cells in presence of 2 X 10(-8) M or 10(-7) M dexamethasone markedly reduced both the membrane-bound and the secreted activities of PA. The extent of reduction depended on the time of addition as well as on the length of exposure to the hormone. A similar concentration of estradiol had no effect on PA activity of the myocytes. Cardiac rat fibroblasts in primary culture showed only the particulate form of the enzyme. Exposure of the fibroblasts to 10(-7) M dexamethasone produced a marked inhibition of this activity. The inhibition of PA activity in medium conditioned by dexamethasone-treated myocytes could be relieved by treatment of the medium with 1% (v/v) sodium dodecyl sulphate (SDS). Digestion with 3.3 micrograms/ml bovine trypsin caused an increase in PA activity of media conditioned with control or dexamethasone-treated cells. The present results indicate that cardiac myocytes and fibroblasts produce PA, and that the modulation of PA by glucocorticoid either involves formation of an inactive PA-protein complex or production of an inactive proenzyme. Since glucocorticoids are often administered in conjunction with fibrinolytic enzymes to re-establish cardial perfusion after thrombosis, the present findings indicate further research to assess potential clinical effects of glucocorticoids through suppression of endogenous PA activity in the heart.
J Mol Cell Cardiol 1986 Nov
PMID:Suppression of plasminogen activator activity by dexamethasone in cultured cardiac myocytes. 294 22

The cardiac sarcoplasmic reticulum preparation employed in this study presented two fractions of associated calmodulin, one easily removable and the other tightly bound. The latter one was resistant to treatment with EGTA and high ionic strength. The forward or hydrolytic component of the (Ca2+, Mg2+)-ATPase cycle of calmodulin-free vesicles was stimulated when preincubated with trypsin, as opposed to the inhibition of this activity when the intact or calmodulin containing vesicles were employed in parallel assays. Interestingly, the reverse reaction of the ATPase cycle or ATP in equilibrium Pi exchange reaction found in both types of vesicles, was more sensitive to exposure to trypsin. Although a drastic inhibition of this exchange reaction was observed independent of the presence of the modulator, this reaction was transiently stimulated when the calmodulin-free vesicles were preincubated with a low trypsin to protein ratio. The differential effect of trypsin upon each reaction indicates that the equilibrium between the E1 and the E2 states of the enzyme is displaced. [125I]calmodulin was found to bind equally to the Ca X E1 approximately P and the E2 - P intermediates of the isolated enzyme formed with the ATP and Pi respectively. It is suggested the formation of an independent overall conformational state for the (Ca2+, Mg2+)-ATPase in the presence of calmodulin.
J Mol Cell Cardiol 1987 Jan
PMID:Independent conformational changes caused by calmodulin and calcium in the cardiac microsomal (Ca2+, Mg2+)-ATPase during its ATP hydrolysis-ATP synthesis cycle. 303 16

Colloidal iron staining, calcium binding and enzyme activities were studied in the isolated rat heart sarcolemma. Colloidal iron staining of the sarcolemma revealed a high density of negatively charged sites associated with the cell surface. This membrane fraction was found to have calcium binding activity at both low (0.1 mM) and high (1.25 mM) concentrations of calcium. Pretreatment of the sarcolemma with either trypsin, phospholipase C or neuraminidase, was associated with a reduction in colloidal iron staining as well as decreased calcium-binding activity at high concentrations of calcium. Calcium binding at low concentrations was decreased by both trypsin and neuraminidase. Mg2+ ATPase, Ca2+ ATPase, and Na+-K+ ATPase activities were altered by neuraminidase and trypsin treatments, whereas phospholipase C treatment altered Na+-K+ ATPase only. It is concluded that both surface negative charge and calcium-binding sites associated with the isolated rat heart sarcolemma are contributed by a mosaic of biomolecules including proteins, phospholipids and glycoproteins, and alterations in the surface charge may influence the activities of membrane-bound enzymes.
Basic Res Cardiol
PMID:Negatively charged sites and calcium binding in the isolated rat heart sarcolemma. 616 50

The Ca2+-dependent ATPase was solubilized from rat heart sarcolemmal membranes upon digestion with trypsin and was found to be different from Ca2+-stimulated Mg2+-dependent ATPase (Dhalla, N. S., Anand-Srivastava, M. B., Tuana, B. S., and Khandelwal, R. L. (1981) J. Mol. Cell. Cardiol. 13, 413-423). The enzyme was purified by high speed centrifugation, ammonium sulfate fractionation, and column chromatography and was seen as a single protein band in nondenaturing polyacrylamide gel electrophoresis. In sodium dodecyl sulfate-acrylamide gels, the enzyme dissociated into two subunits or fragments with molecular weights of about 55,000 and 12,000. The molecular weight of the enzyme, estimated by gel filtration on a Sephadex G-100 column, was found to be about 67,000. The enzyme utilized ATP with a Km of 0.20-0.26 mM but was also able to utilize ITP, CTP, GTP, and ADP as substrates at much lower rates. It was activated by Ca2+ with a Ka of 0.13-0.21 mM; it was also activated by other cations in the order Ca2+ greater than Mn2+ greater than Sr2+ greater than Ba2+ greater than Mg2+. Divalent cations like Cu2+, Ni2+, and Mg2+ were potent inhibitors. The enzyme was insensitive to ouabain, verapamil, oligomycin, cyanide, and vanadate but was markedly inhibited by N-ethylmaleimide. Calmodulin failed to stimulate Ca2+-dependent ATPase and instead inhibited slightly. Unlike K+, Na+ produced a marked inhibition of the Ca2+-dependent ATPase activity, and this inhibition was associated with an 8- 10-fold decrease in the affinity of the enzyme for Ca2+. The competitive action of Na+ indicates that the Ca2+-dependent ATPase may be a site of Na+-Ca2+ antagonism in the cell membrane.
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PMID:Purification and characterization of a Ca2+-dependent ATPase from rat heart sarcolemma. 621 55

In 25 hypertensive patients (15 with renal artery stenosis and 10 with essential hypertension), captopril, in a single 12.5 mg dose, caused a prompt decrease in arterial pressure without changing the heart rate. Plasma active and trypsin-activated renin significantly increases, whereas inactive renin and plasma aldosterone decreased. The plasma active/inactive renin ratio was also increased, suggesting that captopril, together with a release of active renin, may induce an in vivo activation of inactive renin. No correlations were found between blood pressure changes and both pretreatment and captopril-induced variations of active, inactive and trypsin-activated renin or the active/inactive ratio. However, the percent decrease in mean arterial pressure was significantly related to the increase in the active/inactive renin ratio in a group of patients whose blood pressure was brought to normal (r = -0.78; p less than 0.001). This finding suggests the possibility that vasodilating substances, in addition to inhibiting angiotensin II formation, might play some role both in exerting a full effect of captopril on blood pressure and in triggering the in vivo mechanisms of inactive renin activation.
Am J Cardiol 1982 Apr 21
PMID:Active and inactive renin after a single dose of captopril in hypertensive patients. 704 96


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