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)

Intact microsomes isolated from rat liver showed no hexose-6-phosphate dehydrogenase activity, but the enzyme was activated by Triton X-100, deoxycholate, NH4OH, glycine/NaOH, lysophosphatidylcholine, phospholipases A and C, pancreatic lipase and cholesterol esterase, and also by sonic treatment. The enzyme activation by deoxycholate, NH4OH and sonic treatments was solely due to solubilization, while that by phospholipase A appeared to be due to the detergent action of the hydrolysis products. On the other hand, the primary effects of phospholipase C, cholesterol esterase and pancreatic lipase might be accounted for by the partial removal of membrane lipids. The results of washing and trypsin digestion experiments suggested that hexose-6-phosphate dehydrogenase is one of the most firmly bound enzymes among the microsomal proteins. The catalytic properties were the same in the solubilized and the membrane-bound, activated enzymes. Feeding the rats on a high carbohydrate diet altered the extent of enzyme activation by sonication and phospholipase C treatment, suggesting that the microsomal membrane would actually undergo changes in the conformation and/or chemical composition under certain circumstances.
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PMID:Latency of microsomal hexose-6-phosphate dehydrogenase activity. 1 59

Previously, we isolated and characterized unique liposomal-like, cholesterol-rich lipid particles that accumulate in human atherosclerotic lesions. Human plasma low density lipoprotein (LDL) has a molar ratio of total cholesterol to phospholipid (3:1) similar to that of this lesion cholesterol-rich lipid particle. However, LDL is enriched in cholesteryl ester while the lesion lipid particle is enriched in unesterified cholesterol. To examine a possible precursor-product relationship between LDL and the lesion lipid particle, we hydrolyzed the cholesteryl ester core of LDL with cholesterol esterase. Cholesteryl ester hydrolysis occurred only after LDL was treated with trypsin. Trypsin pretreatment was not required for cholesteryl ester hydrolysis of LDL oxidized with copper, a treatment that also degrades apolipoprotein B, the major protein moiety in LDL. In contrast to greater than 90% hydrolysis of cholesteryl ester in trypsin-cholesterol esterase-treated or copper-oxidized LDL, there was only 18% hydrolysis of cholesteryl ester in similarly treated high density lipoprotein. With a limited 10-min hydrolysis of LDL cholesteryl ester, LDL-sized particles and newly formed larger flattened films or discs were present. With complete hydrolysis of LDL cholesteryl ester, LDL particles converted to complex multilamellar, liposomal-like, structures with sizes approximately five times larger than native LDL. These liposomal-like particles derived from LDL were chemically and structurally similar to unesterified cholesterol-rich lipid particles that accumulate in atherosclerotic lesions.
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PMID:Hydrolysis of cholesteryl ester in low density lipoprotein converts this lipoprotein to a liposome. 153 75

A simple and highly specific method for estimating the cholesterol esterase activity is suggested. Cholesterol esterase (EC 3.1.1.13) is incubated with the emulsified substrate, cholesteryl-o-coumarate, at pH 6.6 to yield o-coumaric (trans-2-hydroxycinnamic) acid detected fluorimetrically (lambda exc 363 nm, lambda em 494 nm) at pH 10.4. The fluorescence associated with the unhydrolyzed substrate is negligible. Cholesteryl-o-coumarate is not hydrolyzed by pancreatic lipase, trypsin, or chymotrypsin under the above conditions. About 1 microgram of pancreatic cholesterol esterase can be determined upon 15 min incubation. The substrate was synthesized by condensation of o-acetoxy-trans-cinnamic acid with cholesterol using the di-tert-butyl pyrocarbonate--pyridine--4-dimethylaminopyridine system.
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PMID:[A fluorometric method of determining cholesterol esterase activity]. 180 18

Carboxyl ester lipase was purified from human pancreatic juice. Antisera were raised in rabbits and the monospecificity of the antibody was verified by immunoblotting. The enzyme was present in zymogen granules of acinar cells, in occasional duct cells, and in secretory material in normal pancreas in immunohistochemistry. Also, occasional cells in the epithelium of small intestinal villi but not the granules of Paneth cells, were stained. Decreased and evenly dispersed staining was observed in necrotic acinar cells in acute pancreatitis, whereas the reaction was intensive in plugs in acinar lumina. Interstitial staining was seen around necrotic pancreatic lobules and in areas of fat necrosis. This staining pattern is similar to that obtained with antisera against other lipolytic pancreatic proteins, but differed from that with antisera against trypsin and pancreatic secretory trypsin inhibitor. We conclude that carboxyl ester lipase behaves similarly to the other lipolytic enzymes during acute pancreatitis and that interstitial localization of secretory lipolytic enzymes is characteristic of the necrotizing inflammatory process in pancreas.
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PMID:Carboxyl ester lipase in human tissues and in acute pancreatitis. 268 25

Tetrahydrolipstatin is a specific lipase inhibitor derived from lipstatin, a lipid produced by Streptomyces toxytricini. In addition to pancreatic lipase, it is shown in the present study that tetrahydrolipstatin also inhibits human gastric lipase, carboxyl ester lipase (cholesterol esterase) of pancreatic origin and the closely related bile-salt-stimulated lipase of human milk. It does not inhibit the exocellular lipase from Rhizopus arrhizus or a lipase recently isolated from Staphylococcus aureus. In the presence of a water-insoluble substrate, such as tributyrin, the inhibition has the characteristics of an irreversible inactivation of the uncompetitive type, thus indicating that an enzyme.substrate.inhibitor complex is formed, which cannot undergo further reaction to yield the normal product. This reaction probably takes place at the aqueous/oil interface of the substrate. In aqueous solution, in the absence of substrate, the inhibition of carboxyl ester lipase by tetrahydrolipstatin has the characteristics of being reversible, and finally becomes of a temporary nature analogues to the trypsin-trypsin inhibitor system. It is suggested that an enzyme-inhibitor complex of an acyl-enzyme type is formed that is slowly hydrolysed, with water as the final acceptor, leaving an intact enzyme and an inactive form of the inhibitor. The enzyme thus consumes the inhibitor, which undergoes a chemical conversion, as indicated by a change in mobility in an appropriate thin-layer chromatographic system, indicating an increase in hydrophilicity. Evidence is presented that the reaction product is an acid and that the functional group of tetrahydrolipstatin is the beta-lactone reacting with the active site of the enzyme.
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PMID:Mode of action of tetrahydrolipstatin: a derivative of the naturally occurring lipase inhibitor lipstatin. 316 82

Lateral and transversal distribution of cholesterol ester hydrolase activity in rat liver microsomal membranes has been studied. Total cholesterol ester hydrolase activity was found predominantly (75%) in rough microsomes though specific esterase activities were similar in rough and smooth microsomal fractions. The transversal asymmetry of the enzyme was examined using the criteria of protease sensitivity and latency of mannose-6-phosphate phosphatase. Cholesterol ester hydrolase resulted drastically inhibited by proteolysis with trypsin when microsomal integrity had been previously disrupted with sodium deoxycholate or sodium taurocholate. Under these conditions, most lumenal mannose-6-phosphate phosphatase activity was destroyed. However, cholesterol esterase was unaffected by preincubating microsomes with the detergent alone, which led to the complete expression of latent mannose-6-phosphate phosphatase or by preincubating them with trypsin, where less than a 15% of the lumenal mannose-6-phosphate phosphatase was lost. These findings suggest that cholesterol ester hydrolase activity is located on the lumenal surface of the hepatic microsomal vesicles.
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PMID:Topological studies on rat liver microsomal cholesterol ester hydrolase. 361 28

Five peptides derived from pro-corticotropin/endorphin (pro-ACTH/endorphin), the pituitary corticotroph cell prohormone, were bioassayed with isolated rat adrenocortical cells: alpha- and beta-melanotropin, beta-lipotropin, beta-endorphin, and the amino-terminal region of pro-ACTH/endorphin known as "16k fragment." The effect of each on steroidogenesis was measured at potentially physiological concentrations (0.01-1 nM) in both the absence and presence of varying concentrations of ACTH-(1-24). Of the peptides tested, only 16k fragment, the amino-terminal region of pro-ACTH/endorphin, has a slight but significant potentiating effect on ACTH-(1-24) action. Prior treatment of 16k fragment with trypsin for 30 sec dramatically increases this dose-dependent synergism. Experiments performed in vivo with hypophysectomized female rats indicate that the trypsin digest of 16k fragment stimulates cholesterol ester hydrolase (cholesterol esterase; sterol-ester acylhydrolase, EC 3.1.1.13) activity in the adrenal cortex but fails to activate cholesterol side-chain cleavage. The effect of the trypsinized material can therefore be qualitatively distinguished from that of ACTH-(1-24). When both ACTH-(1-24) and the digest are administered together, a synergistic increase in serum corticosterone concentration results. We propose that a portion of 16k fragment molecule may play a hormonal role in the control of adrenocortical steroidogenesis.
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PMID:Adrenocortical response to corticotropin is potentiated by part of the amino-terminal region of pro-corticotropin/endorphin. 624 28

A computer modeling system developed to analyze experimental data for inactivation of the Escherichia coli alpha-ketoglutarate dehydrogenase complex (KGDC) accompanying release of lipoyl moieties by lipoamidase and by trypsin [Hackert, M.L., Oliver, R.M. & Reed, L.J. (1983) Proc. Natl. Acad. Sci. USA 80, 2226-2230] was used to analyze analogous data for the E. coli pyruvate dehydrogenase complex (PDC). The model studies indicate that the activity of PDC, as found for KGDC, is influenced by redundancies and random processes, which we describe as a multiple random coupling mechanism. In both complexes more than one lipoyl moiety services each pyruvate dehydrogenase (EC 1.2.4.1) or alpha-ketoglutarate dehydrogenase (EC 1.2.4.2) (E1) subunit, and an extensive lipoyl-lipoyl interaction network for exchange of electrons and possibly acyl groups must also be present. The best fit between computed and experimental data for PDC was obtained with a model that has four lipoyl domains with four or, more probably, eight lipoyl moieties servicing each E1 subunit. The lipoyl-lipoyl interaction network for PDC has lipoyl domain interactions similar to those found for KGDC plus the additional possibility of interaction of a lipoyl moiety and its paired mate on each dihydrolipoamide acetyltransferase (EC 2.3.1.12) (E2) subunit. The two lipoyl moieties on an E2 subunit in PDC appear to be functionally indistinguishable, each servicing the acetyltransferase site of that E2 subunit and a dihydrolipoamide dehydrogenase (EC 1.6.4.3) (E3) subunit if the latter is bound to that particular E2 subunit. The observed difference between inactivation of PDC by lipoamidase and by trypsin appears to be due to dead-end competitive inhibition by lipoyl domains that have been modified by excision of lipoyl moieties by lipoamidase.
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PMID:A computer model analysis of the active-site coupling mechanism in the pyruvate dehydrogenase multienzyme complex of Escherichia coli. 634 73

A computer modeling system was used to analyze experimental data for inactivation of the Escherichia coli alpha-ketoglutarate dehydrogenase complex accompanying release of lipoic acid residues by lipoamidase and by trypsin [Stepp, L. R., Bleile, D. M., McRorie, D. K., Pettit, F. H. & Reed, L. J. (1981) Biochemistry 20, 4555-4560]. The results provide insight into the active-site coupling mechanism in the alpha-ketoglutarate dehydrogenase complex. The model studies indicate that the overall activity of the alpha-ketoglutarate dehydrogenase complex is influenced by redundancies and random processes that we describe as a multiple random coupling mechanism. More than one lipoyl moiety services each E1 subunit (alpha-ketoglutarate dehydrogenase, EC 1.2.4.2), and an extensive lipoyl-lipoyl interaction network for exchange of electrons and possibly acyl groups must also be present. The best fit between computed and experimental data was obtained with a model that has two lipoyl moieties servicing each E1 subunit and a lipoyl-lipoyl interaction network that links all lipoyl moieties on the E2 cube (dihydrolipoamide succinyltransferase, EC 2.3.1.61). The single lipoyl moiety on an E2 subunit is assumed to service the coenzyme A-dependent succinyltransferase site of that E2 subunit as well as an E3 subunit (dihydrolipoamide dehydrogenase, EC 1.6.4.3) if the latter is bound to that particular E2 subunit.
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PMID:Evidence for a multiple random coupling mechanism in the alpha-ketoglutarate dehydrogenase multienzyme complex of Escherichia coli: a computer model analysis. 640 46

The relationships between release of (3)H-labeled lipoyl moieties by trypsin and lipoamidase and accompanying loss of overall enzymatic activity of the Escherichia coli pyruvate and alpha-ketoglutarate dehydrogenase complexes were studied. Trypsin releases lipoyl domains together with their covalently attached lipoyl moieties from the "inner" core of the dihydrolipoyl transacetylase and the dihydrolipoyl transsuccinylase whereas lipoamidase releases only the lipoyl moieties. The results show that release of lipoyl domains by trypsin and release of lipoyl moieties by lipoamidase proceeded at faster rates than the accompanying loss of overall activity of the two complexes. Trypsin released about half of the lipoyl domains in the pyruvate dehydrogenase complex without significant effect on the overall activity. A model is presented to explain these and other observations on active-site coupling via lipoyl moieties.
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PMID:Use of trypsin and lipoamidase to study the role of lipoic acid moieties in the pyruvate and alpha-ketoglutarate dehydrogenase complexes of Escherichia coli. 679 98


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