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)

The effects of trypsin, phospholipase A, and chymotrypsin on NADPH-cytochrome c reductase and cytochrome P-450 of microsomes from cryptorchid mouse testes and liver were compared. Trypsin released both enzymes almost completely from testis microsomes, while it readily released only NADPH-cytochrome c reductase from liver microsomes. Chymotrypsin alone, even under conditions where 30-40% of the microsomal protein was hydrolyzed, had little effect on localization or activity of either enzyme in either tissue. Phospholipase A destroyed cytochrome P-450 in testicular microsomes but had little effect on this enzyme in hepatic microsomes or on NADPH-cytochrome c reductase in either preparation. When, however, the microsomes were incubated with chymotrypsin in the presence of a detergent, the effects were similar to those of trypsin alone; testicular cytochrome P-450 was destroyed, while hepatic cytochrome P-450 was only slightly solubilized, and NADPH-cytochrome c reductase from both types of microsomes was both solubilized and activated. From these results we conclude that arginyl and/or lysyl bonds may play a significant role in the junction between the hydrophobic region of the membrane and the anchor region of the reductase molecule and that cytochrome P-450 of testicular microsomes is more superficially located in the lipid bilayer than is hepatic microsomal cytochrome P-450.
...
PMID:The environment of cytochrome P-450 in testicular microsomes. 720 24

NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2) (DT-diaphorase) is a FAD-containing reductase that catalyzes a unique 2-electron reduction of quinones. It consists of 2 identical subunits. In this study, it was found that the carboxyl-terminal portion of the 2 subunits can be cleaved by various proteases, whereas the amino-terminal portion cannot. It was also found that proteolytic digestion of the enzyme can be blocked by the prosthetic group FAD, substrates NAD(P)H and menadione, and inhibitors dicoumarol and phenindione. Interestingly, chrysin and Cibacron blue, 2 additional inhibitors, cannot protect the enzyme from proteolytic digestion. The results obtained from this study indicate that the subunit of the quinone reductase has a 2-domain structure, i.e., an amino-terminal compact domain and a carboxyl-terminal flexible domain. A structural model of the quinone reductase is generated based on results obtained from amino-terminal and carboxyl-terminal protein sequence analyses and electrospray mass spectral analyses of hydrolytic products of the enzyme generated by trypsin, chymotrypsin, and Staphylococcus aureus protease. Furthermore, based on the data, it is suggested that the binding of substrates involves an interaction between 2 structural domains.
...
PMID:A two-domain structure for the two subunits of NAD(P)H:quinone acceptor oxidoreductase. 751 54

Macrophage NO synthase (NOS) is a dimeric enzyme comprising two identical 130 kDa subunits and contains iron protoporphyrin IX (heme), tetrahydrobiopterin, FAD, FMN, and calmodulin. We have carried out limited proteolysis to locate the domains involved in prosthetic group binding and subunit interaction. Trypsin cleaved the subunits of dimeric macrophage NOS at a single locus, splitting the enzyme into two fragments whose denatured molecular masses were 56 and 74 kDa. The smaller fragments remained dimeric in their native form (112 kDa), contained heme and tetrahydrobiopterin, and could bind L-arginine, CO, or imidazole. In contrast, the larger fragments were monomeric in their native form, contained FAD, FMN, and CAM, and bound NADPH. Although neither purified fragment alone or in combination catalyzed NO synthesis from L-arginine, the flavin-containing fragment did catalyze cytochrome c reduction at a rate that was equivalent to that of native dimeric NOS. These results indicate that trypsin cuts macrophage NOS into two domains that can exist and function independently of one another. The domain that binds heme, H4biopterin, and substrate is also responsible for maintaining the NOS dimeric structure, while the domain containing FAD, FMN, and CAM is not required for subunit interaction. This suggests a structural model for macrophage NOS in which the subunits align in a head-to-head manner, with the oxygenase domains interacting to form a dimer and the reductase domains existing as independent extensions.
...
PMID:Macrophage NO synthase: characterization of isolated oxygenase and reductase domains reveals a head-to-head subunit interaction. 753 45

Reduction of ferric iron in the presence of HuTu 80 cells or duodenal microvillus membranes (MVMs) was investigated. With both systems, NADH-dependent reduction of Fe3+/NTA (nitrilotriacetic acid) was demonstrated, using the ferrous iron chelator ferrozine. Uptake of Fe3+ from Fe3+/NTA by HuTu 80 cells was strongly inhibited by addition of ferrozine, indicating that Fe2+ is the substrate for the iron uptake system. With isolated plasma membranes it is shown that the reductase activity is sensitive to trypsin and incubation at 65 degrees C. The reductase activity could be extracted from the plasma membrane and partially purified by ammonium sulphate precipitation and isoelectric focusing. From the purification and inhibition characteristics we conclude that reduction of ferric iron on the surface of duodenal plasma membranes is catalysed by a membrane protein.
...
PMID:Characterization and partial purification of a ferrireductase from human duodenal microvillus membranes. 763 88

Bombesin is known to induce pancreatic growth. In aged animals, reduced responsiveness of tissues of the gastrointestinal tract to a number of hormones/peptides, including bombesin, has been demonstrated, yet the effects of chronic bombesin administration on the aging pancreas is poorly understood. In the present study, groups of 4- and 20- to 22-month-old male Fischer 344 rats were infused by osmotic minipump with saline (control) or bombesin (300 ng/kg/h) for 14 days. In young rats, bombesin administration increased trypsin activity in the pancreas, which was accompanied by an increase in trypsinogen steady-state mRNA levels. However, this response to bombesin was not observed in aged rats. Bombesin also increased pancreatic glutathione peroxidase and reductase, but not superoxide dismutase activity in young rats, whereas activity of these antioxidant enzymes was not affected by bombesin in old rats. These data further support the observation that responsiveness of the pancreas to hormones is diminished with advancing age.
...
PMID:Bombesin-induced changes in expression of pancreatic enzymes in young and old rats. 768 18

NADPH-cytochrome P450 reductase (CPR; NADPH:ferrihemoprotein reductase, EC 1.6.2.4) catalyzes the transfer of electrons to all known microsomal cytochromes P450. CPR is unique in that it is one of only two mammalian enzymes known to contain both flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), the other being the various isoforms of nitric oxide synthase. Similarities in amino acid sequence and in functional domain arrangement with other key flavoproteins, including nitric oxide synthase, make CPR an excellent prototype for studies of interactions between two flavin cofactors. We have obtained diffraction-quality crystals of rat liver CPR, expressed in Escherichia coli and solubilized by limited proteolysis with trypsin. The crystals were grown in Hepes buffer (pH 7.0), containing polyethylene glycol 4500 and NaCl. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell dimensions a = 103.3 A, b = 116.1 A, and c = 120.4 A. If we assume that there are two molecules of the 72-kDa CPR polypeptide per asymmetric unit, the calculated value of Vm is 2.54 A3/Da.
...
PMID:Crystallization and preliminary x-ray studies of NADPH-cytochrome P450 reductase. 772 41

The flavoprotein ferredoxin-NADP reductase (FNR) was isolated from the unicellular green alga, Chlamydomonas reinhardtii. FNR is a monomeric protein containing one FAD and exhibiting ferredoxin-dependent cytochrome c reduction activity. Its complete primary structure was investigated by sequencing overlapping peptides generated by cleavage with trypsin and SV8 protease and confirmed by partial (80%) nucleotidic sequence. C. reinhardtii FNR contains 320 residues, corresponding to a calculated mass of 35,685 and 36,470 including FAD, in agreement with the values measured by laser desorption mass spectrometry. The combination of both amino acid and nucleotidic sequencing, in association with mass spectrometry of peptides, allowed the identification of two N epsilon-trimethyllysines at positions 83 and 89 and one N epsilon-dimethyllysine at position 135. Comparison of the primary structure of C. reinhardtii FNR with the known sequences shows 41-46% identity.
...
PMID:Primary structure and post-translational modification of ferredoxin-NADP reductase from Chlamydomonas reinhardtii. 784 Jun 25

An azidoubiquinone derivative, 3-azido-2-methyl-5-methoxy [3H]-6-decyl-1,4-benzoquinone ([3H]azido-Q), was used to study the ubiquinone-protein interaction and to identify ubiquinone-binding proteins in bovine heart mitochondrial succinate-ubiquinone reductase. When the reductase was incubated with [3H]azido-Q and illuminated with long wavelength UV light, the decrease in the enzymatic activity correlated with the amount of azido-Q incorporated into the protein. When the illuminated, [3H]azido-Q-treated reductase was extracted with organic solvent and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, radioactivity was found primarily in the QPs1 subunit. The [3H]azido-Q-labeled QPs1 was purified from labeled reductase by a procedure involving ammonium sulfate fractionation, dialysis, organic solvent extraction, lyophilization, preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and cold acetone precipitation. The purified, [3H]azido-Q-labeled QPs1 protein was subjected to reductive carboxymethylation prior to digestion by trypsin. One azido-Q-linked peptide, with a retention time of 66.9 min, was obtained by high performance liquid chromatographic separation. The partial amino-terminal sequence of this peptide is GLTISQL-, indicating that this tryptic peptide comprises amino acid residues 113-140 of the revised amino acid sequence of QPs1. The Q-binding domain, using the proposed structure of QPs1, is probably located in the stretch connecting transmembrane helices 2 and 3 that extrude from the surface of the M side of the inner membrane.
...
PMID:Identification of the ubiquinone-binding domain in QPs1 of succinate-ubiquinone reductase. 789 Jul 54

Dehydroascorbate reductase has been isolated from spinach chloroplasts and purified to apparent homogeneity. The N-terminal amino acid sequence of the enzyme is homologous to the Kunitz-type trypsin inhibitors from plant sources. It is shown that spinach DHA reductase and soybean trypsin inhibitor are both capable of reducing dehydroascorbate when in the reduced (thiol) form but acquire trypsin-inhibiting activity in the oxidized (disulfide) state. Reduced chloroplast thioredoxins also reduce dehydroascorbate.
...
PMID:A novel-dehydroascorbate reductase from spinach chloroplasts homologous to plant trypsin inhibitor. 792 67

Progesterone 5 beta-reductase, which catalyzes the reduction of progesterone to 5 beta-pregnane-3,20-dione, was purified 770-fold to homogeneity from the cytosolic fraction of shoot cultures of Digitalis purpurea. This purification involved DEAE-Sephacel, affinity chromatography (Blue-Sepharose CL-6B and adenosine 2',5'-bisphosphate-Sepharose 4B) and elution from a gel matrix after non-dissociating PAGE. The molecular mass determined by SDS/PAGE was 43 kDa and the molecular mass determined by gel-filtration chromatography on calibrated Sephadex G-200 was 280 kDa, thus indicating that the native protein is a polymer consisting of several subunits. The purified enzyme had a Km value of 6 microM for NADPH and 34 microM for progesterone. The enzyme had a strong substrate specificity for progesterone. The relative rates for other steroids such as testosterone, cortisone and cortisol were much lower. The trypsin digestion of the purified progesterone 5 beta-reductase resulted in 100 peptide fragments. The largest fragment after trypsin digestion and sequence analysis consisted of 13 amino acids.
...
PMID:Purification, characterization and partial peptide microsequencing of progesterone 5 beta-reductase from shoot cultures of Digitalis purpurea. 795 3


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

---