Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.27 (thermolysin)
 1,894 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Fluorimetric techniques were used to characterize the environment of tryptophan residues in thermolysin and apo-thermolysin. The apo-thermolysin was obtained by dissolving the enzyme in the presence of 10mm-EDTA, which removed the functional Zn(2+) ion and the four Ca(2+) ions/molecule from the enzyme. 2. At 25 degrees C in aqueous solution the fluorescence-emission spectrum of the native holoenzyme, on excitation at 290nm, was essentially characteristic of tryptophan, with an emission maximum at 333nm. The emission maximum of the apoenzyme is red-shifted to 338nm and the relative intensity of fluorescence is decreased by 10%, both effects indicating some unfolding of the protein molecule, with the indole groups being transferred to a more hydrophilic environment. 3. Fluorescence quenching studies using KI, N'-methylnicotinamide hydrochloride and acrylamide indicated a more open structure in the apoenzyme, with the tryptophan residues located in a negatively charged environment. 4. The thermal properties of the apoenzyme, as monitored by fluorescence-emission measurements, are dramatically changed with respect to the native holoenzyme. In fact, whereas the native enzyme is heat-stable up to about 80 degrees C, for the apoenzyme a thermal transition is observed near 48 degrees C. The apoenzyme is also unstable to the action of unfolding agents such as urea and guanidinium chloride, much as for other globular proteins from mesophilic organisms. 5. The functional Zn(2+) ion does not contribute noticeably to the stability of thermolysin. 6. It is concluded that a major role in the structural stability of thermolysin is played by the Ca(2+) ions, which have a bridging function within this disulphide-free protein molecule.
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PMID:A fluorimetric study of the role of calcium ions in the stability of thermolysin. 41 88

Glia maturation factor from the pig brain can be detected in two molecular forms: the high molecular weight form which is 200 000 dalton in size and the low molecular weight form which is 40 000 dalton in size, as determined by Sephadex gel filtration. The former accounts for 85% of the total biological activity extracted at physiologic pH. The proportion of the low molecular weight form increases following freeze-thawing and ion-exchange chromatography. In addition to the morphological effects, both forms possess mitogenic activity but no esteropeptidase activity. Both forms show similar enzyme susceptibility, being inactivated by papain, ficin and pronase but resistant to subtilisin, thermolysin and trypsin. The high molecular weight form is more resistant to denaturation by low pH, heating and urea than the low molecular weight form. The high molecular weight factor has an isoelectric point of 4.27 whereas the low molecular weight factor has one of 5.04.
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PMID:Multiple molecular forms of glia maturation factor. 46 31

1. When thermolysin was treated with a 100-fold molar excess of 2,4,6-trinitrobenzene-1-sulfonate at pH 8.0 and 37 degrees for 7 h, all 12 amino groups in the enzyme were almost completely trinitrophenylated. The fully trinitrophenylated enzyme still retained more than 80% of its original activity. The amino groups are therefore not essential for activity. 2. When treated with a 100- to 1,000-fold molar excess of N-acetylimidazole at pH 6.5 and 23 degrees for 2 h, thermolysin lost about 54% of its activity with concomitant acetylation of 21 tyrosine residues out of the total of 28 residues. The reaction did not easily proceed any further. This partially inactivated enzyme regained almost full activity upon treatment with hydroxylamine. These modified tyrosine residues are therefore not directly involved in the active site. 3. Thermolysin was not inactivated by treatment with about 100- to 150-fold molar excess of 2-hydroxy-5-nitrobenzyl bromide or dimethyl(2-hydroxy-5-nitrobenzyl)sulfonium bromide at pH 6.0 and room temperature for 1 h both in the presence and absence of 8 M urea. Thus the three tryptophan residues in the enzyme are not accessible to these reagents. When treated with a 4.3- to 43-fold molar excess of N-bromosuccinimide over tryptophan, the enzyme was inactivated to varying extents, depending on the reaction conditions used. In this case, the tyrosine residues appeared to be the most rapidly modified, but tryptophan and histidine residues were also modified with extensive inactivation at higher concentrations of the reagent. The presence of 8 M urea retarded the inactivation.
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PMID:Studies on thermolysin. I. Effects of chemical modifications on the activity of thermolysin. 84 38

Diferric ovotransferrin was hydrolyzed by thermolysin, a thermostable protease, at elevated temperatures. At 65 degrees C, the amino(N)-terminal lobe was completely digested into small peptides, while the carboxyl(C)-terminal lobe was significantly resistant to the protease. This permitted the isolation of an iron-bound C-terminal half-molecule consisting of a glycosylated single polypeptide in an excellent yield (about 90%). The fragment comprises the residues from 336 to the C-terminus of ovotransferrin. The results for the visible absorption spectrum of the copper-bound fragment, the stability of the iron-bound fragment in high concentration of urea, and the CD spectra of the fragment in the far and near UV regions indicated that it retains the metal binding activity and conformation of the C-terminal lobe of intact ovotransferrin.
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PMID:The carboxyl-terminal half-molecule of ovotransferrin prepared by selective digestion of the amino-terminal lobe with thermolysin. 136 35

When synthesized in Escherichia coli, the light-harvesting chlorophyll a/b-binding protein (LHCP) precursor accumulates in inclusion-like bodies (Abad, M. S., Oblong, J. E., and Lamppa, G. K. (1991) Plant Physiol. 96, 1220-1227). In this study we show that after solubilization in 6 M urea and dialysis into 20 mM Tris-HCl (pH 8.0) the recombinant LHCP precursor (preLHCP) was not found as a monomer (31 kDa), but instead produced a heterogeneous population of oligomeric complexes, ranging from 60-300 kDa as determined by gel filtration chromatography. Circular dichroism analysis indicated that the oligomers had folded structure, and that it was composed of both alpha-helix and beta-sheet. Approximately half of recombinant preLHCP found in these complexes was cleavable at the transit peptide-mature protein junction by a soluble chloroplast-processing enzyme in an organelle-free reaction. At 1.5 microM the recombinant precursor inhibited the import of radiolabeled preLHCP and the precursor of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase generated by reticulocyte lysate translations. When chloroplasts were preincubated with the precursor, followed by their reisolation, import was still blocked, providing evidence that competition between recombinant preLHCP and these substrates occurred at the chloroplast per se. Recombinant preLHCP was visualized on the envelope by immunofluorescence microscopy, and its presence there was mediated by a thermolysin-sensitive factor.
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PMID:Precursor for the light-harvesting chlorophyll a/b-binding protein synthesized in Escherichia coli blocks import of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. 162 23

Protamines were extracted from stallion sperm cell nuclei, alkylated with iodoacetamide and separated by reversed-phase high-performance liquid chromatography. Two main components, protamine 1 and protamine 2, were obtained. The latter contains two subspecies, separable by acetic acid-urea-polyacrylamide gel electrophoresis. The primary structure of protamine 2a (St2a) was determined by analysis of fragments obtained from purified protamine 2 peak by thermolysin digestion. The digested peptides were separated by acetic acid-urea gel electrophoresis and, after electroblotting onto a polyvinylidene difluoride filter, their amino acid sequences were determined by pulse liquid peptide sequencing. The amino acid sequence of protamine 2b was predicted from the double sequence data of protamine 2 peak by eliminating the amino acid of St2a in each cycle. St2a and St2b were found to contain 62 and 58 amino acid residues, respectively, and they seem to be homologous with type 2 protamines from human and mouse spermatozoa.
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PMID:Primary structures of two protamine 2 variants (St2a and St2b) from stallion spermatozoa. 236 93

We have investigated the effect in solution of synthetic carrier ampholytes on the saturation of human serum transferrin. By spectrophotometric titrations of human serum transferrin with various Fe3+-carrier ampholyte solutions, we demonstrated that under these conditions carrier ampholytes behave as typical chelators, their binding curves being very similar to that obtained with disodium nitrilotriacetate. On performing titration experiments at three different pH values, carrier ampholytes act like nitrilotriacetate at pH 7.5, but the former are more effective iron donors at pH 8.4 and worse iron donors at pH 5.2. Spectrophotometric titrations of isolated C-terminal and N-terminal fragments obtained from human serum transferrin by thermolysin cleavage show no differences between them, and no differences with respect to the whole protein except that they contain half the number of binding sites. In order to determine a site-specificity of iron in the presence of ampholytes, the classical urea/polyacrylamide-gel-electrophoresis technique was adopted. Under saturating conditions carrier ampholyte solutions act mostly on the C-terminal site, whereas desaturating agents remove iron preferentially from the N-terminal site. Our findings support the hypothesis that Ampholine may chelate Fe3+ as well as many other compounds.
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PMID:Effect of synthetic carrier ampholytes on saturation of human serum transferrin. 273 May 92

A single-sited iron-binding fragment of human transferrin has been obtained by thermolysin cleavage of the protein, selectively loaded with iron in the C-terminal binding site, in a urea-containing buffer. The fragment contains carbohydrate, and hence derives from the C-terminal half of transferrin. Its metal-binding site accepts Fe3+ and Cu2+ with bicarbonate as accompanying anion, but only Fe3+ with oxalate as anion. EPR spectroscopic properties of the fragment are similar to those of the corresponding site in the intact protein. However, iron-binding by the fragment is weaker than by the C-terminal site of the intact protein, particularly at low pH, suggesting that overall as well as local protein conformation influences the metal-binding functions of the site.
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PMID:Preparation and properties of a single-sited fragment from the C-terminal domain of human transferrin. 298 30

Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides is inactivated by trypsin, chymotrypsin, pronase E, thermolysin, 4.0 M urea, and by heating to 49 degrees C. It is protected, to varying degrees, against all these forms of inactivation by glucose 6-phosphate, NAD+, and NADP+. When these ligands are present at 10 times their respective KD concentrations, protection by NAD+ or glucose 6-phosphate is substantially greater than protection by NADP+. A detailed analysis was undertaken of the protective effects of these ligands, at varying concentrations, on proteolysis of glucose-6-phosphate dehydrogenase by thermolysin. This study confirmed the above conclusion and permitted calculation of KD values for NAD+, NADP+, and glucose 6-phosphate that agree with such values determined by independent means. For NADP+, two KD values, 6.1 microM and 8.0 mM, can be derived, associated with protection against thermolysin by low and high NADP+ concentrations, respectively. The former value is in agreement with other determinations of KD and the latter value appears to represent binding of NADP+ to a second site which causes inhibition of catalysis. A Ki value of 10.5 mM for NADP+ was derived from inhibition studies. The principal conclusion from these studies is that NAD+ binding to L. mesenteroides glucose-6-phosphate dehydrogenase results in a larger global conformational change of the enzyme than does NADP+ binding. Presumably, a substantially larger proportion of the free energy of binding of NAD+, compared to NADP+, is used to alter the enzyme's conformation, as reflected in a much higher KD value. This may play an important role in enabling this dual nucleotide-specific dehydrogenase to accommodate either NAD+ or NADP+ at the same binding site.
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PMID:Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides: ligand-induced conformational changes. 329 33

An acid DNase (DNase II) from porcine spleen was purified by sequential chromatography over carboxymethyl-cellulose, blue dextran-Sepharose, hydroxylapatite, and sulfoxyethyl-cellulose. The purified enzyme shows two polypeptide bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis at Mr 35,000 (alpha chain) and 10,000 (beta chain). The sum of the two molecular weights is that of the native enzyme (45,000). Thus, the DNase II molecule is an alpha,beta dimer. The two polypeptides are not joined by disulfide bonds, but can be cross-linked chemically with dimethyl suberimidate. They are dissociable in 8 M urea, after which they can be isolated by gel filtration on Sephadex G-100, eluting with 1 M acetic acid. Once dissociated, the two polypeptides cannot be reassociated to regenerate DNase II activity. The sum of the amino acid compositions of the two polypeptides is that of the native enzyme, and both contain carbohydrate. The beta chain is devoid of histidine, half-cystine, valine, and methionine. The NH2-terminal amino acid of the alpha chain is leucine, while that of the beta chain cannot be identified by either dansylation or Edman degradation. Alkylation of an essential histidine residue of DNase II occurs on incubation of the enzyme with [2-14C] ICH2COOH (Oshima, R. G., and Price, P. A. (1973) J. Biol. Chem. 248, 7522-7526). Radioactivity is found only in the alpha chain. After hydrolysis of the alpha chain with trypsin, chymotrypsin, and thermolysin, radioactive peptides were isolated by gel filtration on Sephadex G-25 and reversed-phase high performance liquid chromatography. Sequence analyses of the radioactive peptides show alkylation of 1 of 9 histidines in the entire amino acid sequence of DNase II. The sequence around this histidine, determined by manual microsequencing and by the release of amino acids with carboxypeptidases A and B, is Ala-Thr-Glu-Asp-His-Ser-Lys-Trp.
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PMID:The subunit structure and active site sequence of porcine spleen deoxyribonuclease. 403 Jul 66


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