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)

Purified cytochrome P-45011 beta from bovine adrenocortical mitochondria was successfully incorporated into the liposome membranes composed of phosphatidylcholine, phosphatidylethanolamine and cardiolipin at a molar ratio of 2:2:1. The incorporation of P-45011 beta into the liposome membranes was ascertained by the Ficoll density gradient centrifugation and the protein refractoriness to trypsin digestion. The prepared proteoliposomes containing P-45011 beta and phospholipid at a molar ratio of 1:3000 were unilamellar vesicles of about 40 nm in average diameter. The P-45011 beta embedded in the liposome membranes was found to be more stable than the detergent-solubilized form. The reconstituted system containing the P-45011 beta-proteoliposomes, adrenodoxin and NADPH-adrenodoxin reductase showed catalytic activities not only for the hydroxylation of 11-deoxycorticosterone at 11 beta- and 18-positions but also for its conversion into aldosterone with a turnover number of 2.3 nmol/min per nmol of P-45011 beta. A successive reaction without the intermediates leaving from the enzyme was suggested for the P-45011 beta-mediated conversion of 11-deoxycorticosterone to aldosterone following the result that the formation of aldosterone was linear with respect to time without the lag phase; this was confirmed by the result that radioactivity in aldosterone from 3H-labeled 11-deoxycorticosterone was scarcely decreased by the addition of unlabeled intermediates to the reactions system.
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PMID:Adrenal cytochrome P-45011 beta-proteoliposomes catalyzing aldosterone synthesis: preparation and characterization. 276 39

The immunochemical relatedness between human and bovine proteins catalyzing the cholesterol side-chain cleavage reaction was investigated. In dot-immunobinding analysis, antibodies against bovine adrenocortical cytochrome P-450SCC, adrenodoxin, and adrenodoxin reductase recognized the corresponding proteins in a dose-dependent manner in mitochondrial preparations from human placenta. Limited proteolysis with trypsin cleaved bovine P-450SCC into fragments F1 and F2, which represent the NH2- and C-terminal parts of P-450SCC, respectively. Identical trypsin treatment yielded similar-size fragments from human placental P-450SCC. In Western immunoblots, anti-F1 and anti-F2 antibodies recognized the corresponding fragments in both trypsin-digested bovine and human P-450SCC. Antibodies against bovine P-450SCC, fragments F1 and F2, adrenodoxin and adrenodoxin reductase inhibited cholesterol side-chain cleavage activity in bovine adrenocortical mitochondria by 24-51%, but failed to affect the activity in human placental mitochondria. These data indicate that human and bovine P-450SCC share common antigenic determinants located outside the enzyme active site. The immunological similarity between bovine adrenodoxin and human ferredoxin allowed for a simple purification protocol of human placental P-450SCC by adrenodoxin affinity chromatography. The P-450SCC obtained by this method was electrophoretically homogeneous and showed characteristics typical to P-450SCC.
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PMID:Comparison of the immunochemical properties of human placental and bovine adrenal cholesterol side-chain cleavage enzyme complex. 279 61

Adrenodoxin, purified from bovine adrenal cortex, was subjected to trypsin cleavage to yield a trypsin-resistant form, designated TT-adrenodoxin. Sequencing with carboxypeptidase Y identified the trypsin cleavage site as Arg-115, while Edman degradation indicated no NH2-terminal cleavage. Native adrenodoxin and TT-adrenodoxin exhibited similar affinity for adrenodoxin reductase as determined in cytochrome c reductase assays. In side chain cleavage assays using cytochrome P-450scc, however, TT-adrenodoxin demonstrated greater activity than adrenodoxin with cholesterol, (22R)-22-hydroxycholesterol, or (20R,22R)-20,22-dihydroxycholesterol as substrate. This enhanced activity is due to increased affinity of TT-adrenodoxin for cytochrome P-450scc; TT-adrenodoxin exhibits a 3.8-fold lower apparent Km for the conversion of cholesterol to pregnenolone. TT-Adrenodoxin was also more effective in coupling with cytochrome P-450(11) beta, exhibiting a 3.5-fold lower apparent Km for the 11 beta-hydroxylation of deoxycorticosterone. In the presence of partially saturating cholesterol, TT-adrenodoxin elicited a type I spectral shift with cytochrome P-450scc similar to that induced by adrenodoxin, and spectral titrations showed that oxidized TT-adrenodoxin exhibited a 1.5-fold higher affinity for cytochrome P-450scc. These results establish that COOH-terminal residues 116-128 are not essential for the electron transfer activity of bovine adrenodoxin, and the differential effects of truncation at Arg-115 on interactions with adrenodoxin reductase and cytochromes P-450 suggest that the residues involved in the interactions are not identical.
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PMID:Adrenodoxin with a COOH-terminal deletion (des 116-128) exhibits enhanced activity. 291 75

Modification of carboxyl groups on putidaredoxin with 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide (EDC) resulted in loss of putidaredoxin reductase activity. The modification did not affect the visible absorption spectrum of putidaredoxin, indicating that the iron-sulfur center was not perturbed. In order to identify the carboxyl groups labeled by EDC, native and EDC-treated putidaredoxin were digested with a combination of trypsin and Staphylococcus aureus protease, and the resulting peptides were separated by high pressure liquid chromatography. The most heavily modified carboxyl groups were found to be those at residues 58, 65, 67, 72, and 77. These carboxyl groups are located in the same general region of the protein as those on adrenodoxin that have been shown to be involved in binding to both adrenodoxin reductase and cytochrome P-450scc. Chemical modification was also used to compare the role of lysine, arginine, and histidine residues on putidaredoxin and adrenodoxin. Modification of lysine and arginine residues had no effect on the reductase activity of either protein. The reductase activity of adrenodoxin was unaffected by labeling with 1 eq of diethyl pyrocarbonate/histidine residue, but labeling with a second equivalent completely abolished both activity and the iron-sulfur center spectrum. In contrast, modification of the 2 histidines in putidaredoxin with 1 eq each resulted in nearly complete loss of reductase activity. There was no significant activity for adrenodoxin in the putidaredoxin reductase assay or for putidaredoxin in the adrenodoxin reductase assay, demonstrating that, in spite of the structural similarity between the two proteins, they are not interchangeable functionally.
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PMID:The involvement of carboxylate groups of putidaredoxin in the reaction with putidaredoxin reductase. 309 90

Treatment of bovine adrenodoxin reductase with trypsin under conditions of limited proteolysis yields two major fragments of apparent molecular weights 30,500 and 20,200. The fragments, which have been partially purified by affinity chromatography to remove most of the intact adrenodoxin reductase, retain adrenodoxin-dependent NADPH cytochrome c reductase activity. Kinetic analyses yield Vmax and Km (adrenodoxin) values of 485 min-1 and 0.96 microM, respectively, at an ionic strength of 0.13 M in comparison to 1059 min-1 and 0.40 microM, respectively, for intact adrenodoxin reductase under the same conditions.
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PMID:Limited proteolysis of bovine adrenodoxin reductase: evidence for a domain structure. 312 75

Modification of bovine adrenodoxin with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) dramatically inhibited the reaction with adrenodoxin reductase (EC 1.18.1.2). The modification did not cause any change in the visible spectrum of adrenodoxin, indicating that the iron-sulfur center was not perturbed. Furthermore, the anomalous fluorescence of Tyr 82 was not changed in either intensity or wavelength. The inhibition was accompanied by the covalent incorporation of 14C-labeled EDC into adrenodoxin. The sites modified by EDC were determined by hydrolyzing adrenodoxin with either trypsin or Staphylococcus aureus protease and separating the resulting peptides by reverse phase high pressure liquid chromatography. The major carboxyl groups modified were found to be at Glu 74, Asp 79, and Asp 86, which are located in a sequence containing a high negative charge density. We propose that the conversion of negatively charged carboxylate groups at these residues to bulky, positively charged EDC-carboxyl groups inhibits the reaction with the reductase. EDC was also found to cross-link adrenodoxin to cytochrome c in yields up to 90%. The cross-links were found to involve the formation of amide linkages between carboxyl groups on adrenodoxin and the lysine amino groups surrounding the heme crevice of cytochrome c.
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PMID:Identification of specific carboxylate groups on adrenodoxin that are involved in the interaction with adrenodoxin reductase. 636 5

Highly specific antibodies against hemeprotein were obtained by immunizing rabbits with a highly purified cholesterol-hydroxylating cytochrome P-450scc from adrenocortical mitochondria. The antibodies do not specifically interact with other components of the adrenocortical electron transport chain, e. g., adrenodoxin reductase and adrenodoxin. Using double immunodiffusion technique (Ouchterlony method), it was shown that the antibodies did not precipitate the microsomal cytochromes P-450 LM2 and LM4, cytochrome b5 and 11 beta-hydroxylating cytochrome P-450 from adrenocortical mitochondria. Antibodies against cytochrome P-450scc inhibited the cholesterol side chain cleavage activity of cytochrome P-450scc in a reconstituted system. Limited proteolysis with trypsin and immunoelectrophoresis in the presence of specific antibodies revealed that antigenic determinants are present of the heme-containing catalytic domain of cytochrome P-450scc (F1) as well as on the domain responsible for the interaction with the phospholipid membrane (F2).
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PMID:[Immunochemical characteristics of cholesterol-hydroxylating cytochrome P-450 from adrenal cortex mitochondria]. 644 2

Bovine adrenocortical cytochrome P450scc (CYP11A1) was selectively modified with diiodofluorescein iodoacetamide (DIFIA). Only Cys264 is labeled in the P450 polypeptide chain. The modification significantly affected the cholesterol-hydroxylating activity in the reconstituted system containing NADPH, adrenodoxin reductase, adrenodoxin, and soluble or membrane-bound P450scc. The inhibitory effect correlates with decreased affinity of cytochrome P450scc to intermediate electron carrier, adrenodoxin. Cytochrome P450scc is modified in liposomes and the modified membrane-bound protein is cleaved by trypsin forming two large fragments F1 and F2 corresponding to the N- and C-terminal regions of the molecule. The data indicate that the Cys264-containing region of the cytochrome P450scc molecule is exposed to the surface of protein globule, located outside of the membrane, and can participate in protein-protein interactions.
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PMID:[Selective chemical modification of cytochrome P450scc (CYP11A1) with diiodofluorescein iodoacetamide in the study of the role and topology of interdomain hinge of the hemoprotein molecule]. 915 54

Optimization of the conditions for heterologous expression of recombinant cytochrome P450scc in E. coli provided an expression level of about 420 nmoles of cytochrome P450scc per liter of bacterial culture. A new procedure for purification of recombinant protein in substrate-bound high-spin and substrate-free low-spin form is described. Highly purified electrophoretically homogeneous recombinant cytochrome P450scc contains 12.3 and 16.7 nmoles heme per mg protein for substrate-free and substrate-bound forms, respectively. The recombinant and natural cytochrome P450scc from bovine adrenocortical mitochondria were compared functionally and immunochemically. The dissociation constants for the complexes of cytochrome P450scc with cholesterol and adrenodoxin, the efficiency of enzymatic reduction in the reconstituted system (NADPH--adrenodoxin reductase--adrenodoxin), and cholesterol side-chain cleavage activity were determined. It was found that limited proteolysis of the recombinant cytochrome P450scc with trypsin forms two main fragments which are electrophoretically and immunochemically identical with the fragments F1 (29.8 kD) and F2 (26.6 kD) formed during proteolysis of bovine adrenocortical cytochrome P450scc. The quantitative values of the studied parameters are practically identical in natural and substrate-bound recombinant cytochrome P450scc, while there were great differences between substrate-bound and substrate-free forms of recombinant cytochrome P450scc both of functional (decrease of cholesterol side-chain cleavage activity, efficiency of enzymatic reduction in the reconstituted system, and affinity to adrenodoxin for substrate-free cytochrome P450scc) as well as structural (increase in accessibility to exogenous and endogenous proteolysis) character. The identity of the folding process for recombinant and natural proteins as well as the nature of a stabilizing and activating effect of cholesterol on cytochrome P450scc is discussed.
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PMID:Comparative structural and immunochemical characterization of recombinant and natural cytochrome p450scc (CYPXIAI). 952 19

Approximately 30% of naturally occurring proteins are predicted to be embedded in biological membranes. Nevertheless, this group of proteins is traditionally understudied due to limitations of the available analytical tools. To facilitate the analysis of membrane proteins, the analytical methods for their soluble counterparts must be optimized or modified. Multiple reaction monitoring (MRM) assays have proven successful for the absolute quantification of proteins and for profiling protein modifications in cell lysates and human plasma/serum but have found little application in the analysis of membrane proteins. We report on the optimization of sample preparation conditions for the quantification of two membrane proteins, cytochrome P450 11A1 (CYP11A1) and adrenodoxin reductase (AdR). These conditions can be used for the analysis of other membrane proteins. We have demonstrated that membrane proteins that are tightly associated with the membrane, such as CYP11A1, can be quantified in the total tissue membrane pellet obtained after high-speed centrifugation, whereas proteins that are weakly associated with the membrane, such as AdR, must be quantified in the whole tissue homogenate. We have compared quantifications of CYP11A1 using two different detergents, RapiGest SP and sodium cholate, and two different trypsins, sequencing grade modified trypsin and trypsin, type IX-S from porcine pancreas. The measured concentrations in these experiments were similar and encouraged the use of either combination of detergent/trypsin for quantification of other membrane proteins. Overall, the CYP11A1 and AdR quantified in this work ranged from 110 pmol to 10 fmol per milligram of tissue protein.
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PMID:Optimizing the conditions of a multiple reaction monitoring assay for membrane proteins: quantification of cytochrome P450 11A1 and adrenodoxin reductase in bovine adrenal cortex and retina. 2052 25


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