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

The complete amino acid sequence of phosphlipase A2 (EC 3.1.1.4) from horse pancreas was determined. The protein controls of a single polypeptide chain of 125 amino acids and has a molecular weight of 13,927. The chain is crosslinked by seven disulfide bridges. The sequence was determined by automated Edman degradation of the intact protein and several of the large peptide fragments. Smaller peptides were analyzed by manual Edman degradation. Fragmentation of the peptide chain was accomplished by enzymatic digestion with trypsin, chymotrypsin, and thermolysin. The final overlap was found by digestion of the polypeptide with a staphylococcal protease specific for glutamoyl bonds. Phospholipase A2 from horse pancreas shows homology to snake venom phospholipases A2 and to the enzyme from porcine pancreas, provided that the published amino acid sequence of the porcine phospholipase A2 is revised to some extent.
 ...
PMID:Amino acid sequence of phospholipase A2 from horse pancreas. 83 12

Morphologically and functionally intact mitochondria were isolated from the porcine pancreas using a conventional, differential centrifugation method. The homogenate of the porcine pancreas made in a medium containing 0.25 M sucrose, 10 mM Tris-Cl, pH 7.4, 0.5% bovine serum albumin and 1 mM EDTA, in the presence or in the absence of dibucaine and trypsin inhibitor, was centrifuged for 10 min at 700xg. The supernatant was centrifuged for 10 min at 7000xg, and the pellet was washed three times. Trypsin activity of mitochondria isolated in the absence of dibucaine and trypsin inhibitor was as low as that of mitochondria isolated in the presence of dibucaine and trypsin inhibitor, and a major part of the activity remained inactivated. Phospholipase A2 activity of the former mitochondria was as low as that of the latter, and remained unchanged up to 8-10 hr at 4 degrees C. The presence of bovine serum albumin and EDTA in the respiration medium was absolutely required to obtain good respiratory controls of those mitochondria. These data suggest that well-coupled mitochondria can be obtained from the pancreas by a conventional isolation procedure without activating the major part of trypsin.
 ...
PMID:Isolation and some biochemical properties of porcine pancreas mitochondria. 151 53

Storage triacylglycerols (TAG) in plant seeds are present in small discrete intracellular organelles called oil bodies. An oil body has a matrix of TAG, which is surrounded by phospholipids (PL) and alkaline proteins, termed oleosins. Oil bodies isolated from mature maize (Zea mays) embryos maintained their discreteness, but coalesced after treatment with trypsin but not with phospholipase A2 or C. Phospholipase A2 or C exerted its activity on oil bodies only after the exposed portion of oleosins had been removed by trypsin. Attempts were made to reconstitute oil bodies from their constituents. TAG, either extracted from oil bodies or of a 1:2 molar mixture of triolein and trilinolein, in a dilute buffer were sonicated to produce droplets of sizes similar to those of oil bodies; these droplets were unstable and coalesced rapidly. Addition of oil body PL or dioleoyl phosphatidylcholine, with or without charged stearylamine/stearic acid, or oleosins, to the medium before sonication provided limited stabilization effects to the TAG droplets. High stability was achieved only when the TAG were sonicated with both oil body PL (or dioleoyl phosphatidylcholine) and oleosins of proportions similar to or higher than those in the native oil bodies. These stabilized droplets were similar to the isolated oil bodies in chemical properties, and can be considered as reconstituted oil bodies. Reconstituted oil bodies were also produced from TAG of a 1:2 molar mixture of triolein and trilinolein, dioleoyl phosphatidylcholine, and oleosins from rice (Oryza sativa), wheat (Triticum aestivum), rapeseed (Brassica napus), soybean (Glycine max), or jojoba (Simmondsia chinensis). It is concluded that both oleosins and PL are required to stabilize the oil bodies and that oleosins prevent oil bodies from coalescing by providing steric hindrance. A structural model of an oil body is presented. The current findings on seed oil bodies could be extended to the intracellular storage lipid particles present in diverse organisms.
 ...
PMID:Surface structure and properties of plant seed oil bodies. 156 29

Morphological features of Manduca sexta plasma lipid transfer particle (LTP) have been investigated by electron microscopy. LTP was found to be an asymmetric particle with two major structural features: a roughly spherical head and an elongated, hinged tail. The hinge occurs approximately at the midpoint of the tail section with the two halves forming angles ranging from 30 degrees to 180 degrees. A molecular mass estimate of 1.4 x 10(6) daltons based on the dimensions of LTP suggests that multiple copies (two or three) of each of the three LTP apoproteins exist in the native complex. Limited digestion studies of LTP suggest that apoLTP-III is less susceptible to trypsin cleavage than apoLTP-I or -II, and therefore may be less exposed to the aqueous environment. Digestion for 1 h at a 1:50 trypsin-LTP protein ratio did not alter the flotation properties of LTP or its morphological features; thus, although significant proteolysis occurred, the particle retained its overall structure. Transfer activity, on the other hand, was affected by trypsin digestion with 30 +/- 14% inhibition of LTP activity occurring upon proteolysis at a 1:50 trypsin-LTP protein ratio. Treatment of LTP with phospholipase A2 resulted in the conversion of LTP-associated phosphatidylcholine and phosphatidylethanolamine to their corresponding lyso forms. Phospholipase A2 treatment did not, however, alter the SDS-PAGE profile, transfer activity, flotation pattern, or the microscopic features of LTP. These results suggest that the products of the phospholipase reaction remain associated with the particle.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Studies of the morphology and structure of the plasma lipid transfer particle from the tobacco hornworm, Manduca sexta. 238 Jun 35

Phospholipase A2 (PLA2; phosphatide 2-acylhydrolase, EC 3.1.1.4) activity from human platelets increases significantly when the enzyme is separated from an endogenous inhibitor(s). The inhibitor, associated mainly with a particulate fraction, has now been identified as a mixture of unsaturated fatty acids. Treatment of the inhibitor with trypsin, RNase, DNase, or heat did not diminish its inhibitory activity, which was extractable by organic solvents. Incubation of PLA2 with phospholipids or various neutral lipids, including saturated fatty acids, had little or no effect on enzymatic activity. In contrast, unsaturated fatty acids such as palmitoleic acid (16:1), oleic acid (18:1), linoleic acid (18:2), linolenic acid (18:3), arachidonic acid (20:4), all of which were detected in the particulate fraction, or longer chained unsaturated fatty acids inhibited PLA2 activity by 50% at approximately equal to 5 X 10(-7) M. The level of unsaturated fatty acids in the inhibitor fraction was equivalent to approximately equal to 10(-4) M, apparently sufficient to effectively inhibit PLA2 activity. Methylation of unsaturated fatty acids caused a complete loss of inhibitory activity, and subsequent demethylation restored the activity, suggesting that a free carboxyl group was necessary. Inhibition of PLA2 by unsaturated fatty acids appeared to be noncompetitive. PLA2 absolutely required Ca2+ for activity; the inhibition by unsaturated fatty acids was not reversed by Ca2+. The finding that unsaturated fatty acids are potent inhibitors of PLA2 would explain its generally low activity in human platelet extracts and its marked increase of activity during the course of enzyme purification.
 ...
PMID:Inhibition of human platelet phospholipase A2 activity by unsaturated fatty acids. 385 56

Treatment with phospholipase C strongly protected monkey kidney (Vero) cells against diphtheria toxin and reduced the ability of the cells to bind 125I-labelled toxin. Treatment with phospholipase D and with trypsin also protected the cells, although to a lesser extent. Phospholipase A2 had no protective effect. Phospholipase C also protected fetal hamster kidney cells against the toxin. After removal of the enzymes, as well as after treatment of the cells with 4-acetamide 4'-isothiocyanostilbene 2,2'-disulfonic acid, diphtheria toxin binding capability was restored slowly, apparently by a process requiring protein synthesis, since cycloheximide blocked the restoration. The data indicate that both phospholipids and protein are involved in the binding sites for diphtheria toxin.
 ...
PMID:Evidence that membrane phospholipids and protein are required for binding of diphtheria toxin in Vero cells. 404 83

FOY-305, a synthetic inhibitor of serin-proteases, shows a highly specific inhibition of the activity of purified trypsin and tryptic activity from duodenal juice in a range of 1 to 10 microM. Phospholipase A2 is only partly inhibited (40%) by much higher concentrations of FOY-305 (100 microM to 1 mM), amylase activity is not affected by either concentrations. FOY-305 did not influence CCK-stimulated amylase- and trypsin-secretion from isolated pancreatic lobules in concentrations which inhibited completely tryptic activity.
 ...
PMID:[Effect of FOY-305 on the activity and secretion of pancreatic enzymes in vitro]. 620 21

Human brain and liver mitochondria contain membrane-bound monoamine oxidase of both A and B types. Monamine oxidase-A (MAO-A), either membrane-bound or in detergent-solubilized extracts from these tissues, was selectively inhibited during incubations with trypsin, chymotrypsin, thermolysin, or papain. MAO-A in solubilized, but not in membrane-bound, preparations was also very sensitive to the action of phospholipase A2, while MAO-B was unaffected. Membrane-bound MAO-A of rat brain mitochondria was more sensitive to phospholipases and less sensitive to proteases than was human brain enzyme, indicating that these agents may reveal species differences in MAO properties. Human brain and liver MAO-A, either solubilized or bound in mitochondrial membranes, apparently contains basic and aromatic peptide moieties that are available to proteases. Hydrolysis of these peptide bonds leads to rapid denaturation unless substrate molecules stabilize the active site. Phospholipase A2 may disrupt the phospholipid microenvironment of MAO-A, the integrity of which is essential for MAO-A activity, but not for MAO-B. No interconversion of the two activities was observed. After phospholipase A2 treatment, remaining MAO-A activity was recovered in low-molecular-weight regions of a gel filtration gradient, suggesting that MAO-A subunits were released. Although these experiments argue against the proposal that phospholipids may regulate the ratio of A/B activities of a single enzyme molecule, it is conceivable that endogenous phospholipases or proteases in mitochondrial membranes may influence MAO-A activity independently of MAO-B activity.
 ...
PMID:Selective effects of proteases and phospholipase A2 on monoamine oxidases A and B of human brain and liver. 637 37

Rat pancreatic islets have been shown to possess specific binding sites for 125I-labeled insulin. Enzymatic and chemical modification of islets are used to reveal important structures and chemical groups for insulin binding. pretreatment with trypsin, neuraminidase, 1-ethyl-3-(3-dimethylamino)carbodiimide (a carboxyl reagent), tetranitromethane (a tyrosyl and thiol reagent), and 1,3-difluoro-4,6-dinitrobenzene (modification of protein functional groups) decreased binding of insulin. This was due to the diminuation of the receptor number; in the case of trypsin-pretreatment also the receptor affinity was decreased. Inhibition of insulin binding was in each case associated with a decrease of the inhibitory effect of exogenous insulin on glucose-induced insulin secretion (not measured in the case of difluorodinitrobenzene and tetranitromethane). Phospholipase A2, (cleavage of phospholipids) did not affect these parameters. 5,5'-dithiobis(2-nitrobenzoic acid) (Ellman's reagent) and possibly p-chloromercuribenzoate (both thiol reagents) increased the number of receptors and decreased receptor affinity, but did not influence the inhibitory effect of insulin on insulin release. It is concluded that protein functional groups, sialic acid, carboxyl and tyrosyl groups, but no phospholipids and probably not sulfhydryl groups are important for the interaction of insulin with insulin receptors of rat pancreatic islets.
 ...
PMID:Properties of the insulin receptor of rat pancreatic islet. 704 7

Inside-out vesicles (IOV) were prepared from human red blood cells. Steady-state uptake of 23Na was observed to generally follow an exponential time course with a rate constant of 1.57 +/- 0.09 h-1 (SE). One week of cold storage (0-4 degrees C) increased the rate constant to 2.50 +/- 0.12 h-1 (SE). Mg2+, Ca2+, or Sr2+ decreased the rate of 22Na uptake with no observable differences between the three divalent cations when tested at concentrations of 50 microM. Mg2+ was shown to decrease the rate of 22Na uptake at concentrations as low as 5 microM with maximal effect at 50 to 100 microM. The decrease in rate of 22Na uptake induced by Mg2+ could be enhanced by exposure of IOV to Mg2+ for longer periods of time. Trypsin treatment of OIV increased the rate of uptake of 22Na and was dependent on the concentration of trypsin added between 5 to 25 micrograms/ml (treated for 5 min at 25 degrees C). The ability of Mg2+ (50 microM) to decrease the rate of 22Na uptake was still observed after maximal trypsin treatment. Phospholipase A2 or phospholipase C treatment of IOV increased the rate of 22Na uptake and was dependent on the amount of phospholipase A2 (0.1 to 1.0 units/ml) or phospholipase C (0.25 to 2.5 units/ml) added (treated for 5 min at 25 degrees C). After phospholipase A2 treatment, the observed decrease in the rate of 22Na uptake induced by Mg2+ (50 microM) was generally greater than controls. After phospholipase C treatment, the observed decrease in rate of 22Na uptake induced by Mg2+ (50 microM) was less or absent when compared with controls. Phospholipase C treatment was less effective in preventing the Mg2+ effect the longer IOV were exposed to Mg2+. The results suggest that Mg2+ binds to phospholipid headgroups to reduce Na permeability perhaps by inducing a change in bilayer structure or phospholipid association.
 ...
PMID:Effects of divalent cations, trypsin, and phospholipases on the passive permeability to sodium of inside-out vesicles from human red cells. 706 86


1 2 Next >>