Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

delta-Aminolaevulinic acid dehydratase catalyses the synthesis of porphobilinogen. The enzyme has a molecular mass of 285000 and is composed of eight similar subunits of molecular mass 35000. The N-terminal amino acid is acylated, and the number of peptides found on tryptic digestion equals the number of lysine and arginine residues per mass of 35000. The eight subunits are apparently arranged at the corners of a cube and therefore have dihedral (D4) symmetry. The bovine liver enzyme which has been cystallized contains 4--6 atoms of zinc per mole of enzyme. The apo-enzyme obtained on prolonged hydrolysis can be reactivated by the addition of zinc or cadmium ions. The dialysed enzyme must be first treated with dithiothreitol. There are two very active SH groups in a total of 6--7-SH groups per subunit. The substrate forms a Schiff base with the epsilon-amino group of a lysine residue. Reduction of the Schiff base with NaBH4 should reveal the number of active sites per mole of enzyme. It appears that only four of the eight subunits form a Schiff base with the substrate indicating that the enzyme exhibits the phenomenon of either half-site reactivity or negative cooperativity. The enzyme appears to have a strong subunit-subunit interaction for an immobilized preparation remained stable for at least a month. An immobilized enzyme preparation was treated in a manner so that it dissociated into tetramers. Both the eluate and protein still attached to the Sepharose on a column were enzymically active. The bound enzyme could not reassociate under assay conditions but still contained about 50% of the original enzyme activity. It would seem that the enzyme is active when composed with less than eight subunits.
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PMID:5-Aminolaevulinic acid dehydratase: structure, function, and mechanism. 0 32

Alkaline phosphatase of Escherichia coli, isolated by procedures which do not alter its intrinsic metal content, contains 4.0 +/- 0.3 g-atoms of tightly bound zinc per mole (Kd less than 1 muM) and 1.3 +/- 0.2 g-atoms of magnesium per mole (Bosron, W.F., Kennedy, F.S., and Vallee, B.L. (1975), Biochemistry 14, 2275-2282). Importantly, the binding of magnesium is dependent both upon pH and zinc content. Hence, the failure to assign the maximal magnesium stoichiometry to enzyme isolated by conventional procedures may be considered a consequence of the conditions chosen for optimal bacterial growth and purification of the enzyme which are not the conditions for optimal binding of magnesium to alkaline phosphatase. Under the conditions employed for the present experimental studies, a maximum of six metal sites are available to bind zinc and magnesium, i.e., four for zinc and two for magnesium. Magnesium alone does not activate the apoenzyme, but it regulates the nature of the zinc-dependent restoration of catalytic activity to apophosphatase, increasing the activity of enzyme containing 2-g-atoms of zinc five-fold and that of enzyme containing 4-g-atoms of zinc 1.4-fold. Moreover, hydrogen-tritium exchange reveals the stabilizing effects of magnesium on the structural properties of phosphatase. However, neither the KM for substrate nor the phosphate binding stoichiometry and Ki are significantly altered by magnesium. Hence, magnesium, which is specificially bound to the enzyme, both stabilizes the dynamic protein structure and regulates the expression of catalytic activity by zinc in alkaline phosphatase.
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PMID:Effect of magnesium on the properties of zinc alkaline phosphatase. 1 22

The guanylate cyclase activity of axoneme--basal apparatus complexes isolated from bovine retinal rods has been investigated. The Mg2+ and Mn2+ complexes of GTP4- serve as substrates. Binding of an additional mole of Mg2+ or Mn2+ per mole of enzyme is required. Among cations which are ineffective are Ca2+, Ni2+, Fe2+, Fe3+, Zn2+, and Co2+. The kinetics are consistent with a mechanism in which binding of Mg2+ or Mn2+ to the enzyme must precede binding of MgGTP or MnGTP. The apparent dissociation constants of the Mg--enzyme complex and the Mn--enzyme complex are 9.5 x 10(-4) and 1.1 x 10(-4) M, respectively. The apparent dissociation constants for binding of MgGTP and MnGTP to the complex of the enzyme with the same metal are 7.9 x 10(-4) and 1.4 x 10(-4) M, respectively. The cyclase activity is maximal and independent of pH between pH 7 and 9. KCl and NaCl are stimulatory, especially at suboptimal concentrations of Mg2+ or Mn2+. Ca2+ and high concentrations of Mg2+ and Mn2+ are inhibitory. Ca2+ inhibition appears to require the binding of 2 mol of Ca2+ per mol of enzyme. The dissociation constant of the Ca2--enzyme complex is estimated to be 1.4 x 10(-6) M2. The axoneme--basal apparatus preparations contain adenylate cyclase activity whose magnitude is 1--10% that of the guanylate cyclase activity.
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PMID:Guanylate cyclase of isolated bovine retinal rod axonemes. 4 May 95

Angiotensin-converting enzyme has been solubilized from a particulate fraction of rabbit lung and purified to apparent homogeneity in 11% yield by a procedure including fractionation with DEAE-cellulose and calcium phosphate gel, elution from Sephadex G-200, and lectin affinity chromatography. The molecular weight estimated by equilibrium sedimentation was approximately 129,000, either in the absence or presence of 6 M guanidine hydrochloride. A slightly higher value of 140,000 determined for the reduced, denatured protein by gel electrophoresis in the presence of sodium dodecyl sulfate and a much higher figure derived from gel filtration are probably due to the glycoprotein nature of the enzyme. Its oligosaccharide content accounted for 26% of the weight calculated from its amino acid and carbohydrate composition. The estimated content of sugar residues per mole was: galactose, 57; N-acetylglucosamine, 53; mannose, 43; N-acetylneuraminic acid, 19; and fucose, 4. Threonine and alanine were identified, respectively, as NH2-terminal and COOH-terminal residues by the dansylation procedure and by digestion with carboxypeptidase A. The enzyme was found to contain approximately 1 g atom of zinc per mol. Km values for hydrolysis of hippurylhistidylleucine and angiotensin I were 2.3 and 0.07 mM, and the corresponding turnover numbers were 15,430 and 792 mol/min/mol at 37 degrees. Bradykinin was also a substrate, and release of its COOH-terminal dipeptide, Phe-Arg, was catalyzed at a comparable rate to that of His-Leu from the COOH terminus of angiotensin I. Enzyme activity required the presence of chloride ions and was inhibited by EDTA and by low concentrations of Bothrops bradykinin-potentiating peptides. In addition, hydrolysis of hippurylhistidylleucine was inhibited competitively by other defined peptides, including di- and tripeptides, which were not substrates.
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PMID:Pulmonary angiotensin-converting enzyme. Structural and catalytic properties. 16 57

Several arginine-rich cationic proteins previously isolated from granules of leukemic myeloid cells have been found to reside primarily in human eosinophil leukocytes. The major component has a molecular weight of 21,000 and it contains approximately 2.6 moles of zinc per mole of protein. Velocity centrifugation of cytoplasm from leukocytes of patients with marked eosinophilia showed that this group of proteins is packaged in the crystalloid-containing large eosinophil granules. Approximately 30% of the protein content of eosinophil granules belonged to this group of cationic proteins. Bactericidal or esterolytic activities of the cationic proteins were not detected, nor did they inhibit guinea pig anaphylatoxin or histamine-induced contraction. The basic protein previously demonstrated in guinea pig eosinophils may be analogous to the group of basic proteins of human eosinophils but great differences are found for molecular weight and amino acid composition.
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PMID:Arginine-rich cationic proteins of human eosinophil granules: comparison of the constituents of eosinophilic and neutrophilic leukocytes. 19 10

Immunogenic and antigenic properties of a Zn2+ -deficient alkaline phosphatase produced in a mutant (U-47) of Escherichia coli have been studied. The native U-47 enzyme, that exists in a monomerdimer equilibrium, was used as immunogen. From the antisera obtained, four antibody populations directed to the various molecular forms of U-47 enzyme have been purified by affinity chromatography using specific antigens coupled to glutaraldehyde-activated beads of indubiose. 70% of the total antibody obtained was directed both to the monomeric and the dimeric forms, 9% was directed to the dimer but showed a low affinity for the monomer; 10% and 11% were specifically directed respectively to the monomer and the dimer. Each antibody population purified had a specific effect on the catalytic activity of the Zn2+ -activated U-47 enzyme. The anti-monomer-dimer and the anti-dimer-monomer inhibit to the same extent whereas the specific anti-monomer does not alter the activity significantly and the specific anti-dimer causes a 30% activation. The catalytic activity of the alkaline phosphatase produced in wild-type strains was also reduced by these anti-U-47 enzyme antibodies. However, whereas the anti-monomer had again very little effect, the anti-dimer-monomer and the anti-monomer-dimer inhibited this enzyme to different extents. The specific antidimer also inhibited this wild-type alkaline phosphate. Antibodies of high affinity to the dimeric form of U-47 enzyme, i.e. specific anti-dimer or anti-dimer-monomer, caused a 30% activation when they were added prior to the reactivation process by Zn2+. Specific anti-monomer strongly inhibited this reactivation process. The Fab fragment of the anti-wild-type phosphatase antibody, under the same conditions, caused a 300% activation. The extents of interactions of the various molecular forms of U-47 enzyme and of the wild-type enzyme with the anti-monomer-dimer and with the anti-dimer have been determined. U-47 enzyme monomeric form has three determinants exposed and the dimeric form has five determinants exposed for interacting with the anti-monomer-dimer antibody, the free wild-type enzyme has only two determinants exposed to this antibody. These determinants might be close to the active site or in another critical location since this antibody can reduce the catalytic activity of the wild-type enzyme to half the original value. The anti-dimer antibodies can interact with three determinants exposed at the surface of the free Zn2+ -reactivated U-47 enzyme and the non-covalent binding of one mole of inorganic phosphate results in the exposure of one more antigenic determinant.
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PMID:Effects of antibodies to various molecular forms of a mutationally altered Escherichia coli alkaline phosphatase on its activation by zinc. 78 17

Kinetic experiments were made with pepsin in the presence of Cu2+ ions and additional Fe2+, Ni2+ or Zn3+ ions as sulphates. As a parameter of the pepsin activity the turnover-rate curves were determined with haemoglobin as a substrate. An important activation of the pepsin was obtained by Cu2+ additions of 5-10(-4) mole/1. When Cu2+ and Fe2+ ions were added to the reaction mixture at the same time, an additive effect of both metal cations was observed. A competitive effect of both metal cations was found in the combination of Cu2+/Ni2+ ions. Zn2+ addition did not influence the activation of pepsin caused by Cu2+ ions.
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PMID:[Interactions between various transition elements in their effect on pepsin activity]. 79 2

Human carboxypeptidase B fraction II has been purified from pancreatic juice by DEAE-'Sephadex' chromatography, isoelectric focusing, and 'Sephadex' G-100 gel filtration. The enzyme has been characterized by analytical polyacrylamide disc-gel electrophoresis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, amino acid analysis Km determination, molecular weight determination on 'Sephadex' G-100, zinc analysis, and inhibition by metal chelating agents. Human carboxypeptidase B fraction II appeared homogeneous in analytical polyacrylamide disc-gel electrophoresis, but showed two components of 23,500 and 9,200 daltons in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Zinc analysis revealed 0.96 gram atoms of zinc per mole of enzyme, and a Km of 65 +/- 3 muM was determined for hydrolysis of hippuryl-L-arginine.
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PMID:Human pancreatic carboxypeptidase B. I. Isolation, purification, and characterization of fraction II. 80 47

D-Ribulose-1,5-bisphosphate (RuBP) carboxylase has been purified from glutamate-CO2-S2O3(2)-grown Thiobacillus intermedius by pelleting the enzyme from the high-speed supernatant and by intermediary crystallization followed by sedimentation into a discontinuous 0.2 to 0.8 M sucrose gradient. The enzyme was homogeneous by the criteria of electrophoresis on polyacrylamide gels of several acrylamide concentrations, sedimentation velocity and equilibrium measurements, and electron microscopic observations of negatively stained preparations. The molecular weights of the enzyme determined by sedimentation equilibrium and light-scattering measurements averaged 462,500 +/- 13,000. The enzyme consisted of closely similar or identical polypeptide chains of a molecular weight of 54,500 +/- 5,450 determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The S(0)20,w of the enzyme was 18.07S +/- 0.22. Electron microscopic examination suggested that the octomeric enzyme (inferred from the molecular measurements mentioned) had a cubical structure. The specific activity of the enzyme was 2.76 mumol of RuBP-dependent CO2 fixed/min per mg of protein (at pH 8 and 30 C), and the turnover number in terms of moles of CO2 fixed per mole of catalytic site per second was 2.6. The enzyme was stable for 3 months at -20 C and at least 4 weeks at 0 C. The apparent Km for CO2 was 0.75 mM, and Km values for RuBP and Mg2+ were 0.076 and 3.6 mM, respectively. Dialyzed enzyme could be fully reactivated by the addition of 20 mM Mg2+ and partially reactivated by 20 mM Co2+, but Cd2+, Mn2+, Ca2+, and Zn2+ had no effect. The compound 6-phosphogluconate was a linear competitive inhibitor with respect to RuBP when it had been preincubated with enzyme, Mg2+, and HCO3-.
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PMID:Purification, quaternary structure, composition, and properties of D-ribulose-1,5-bisphosphate carboxylase from Thiobacillus intermedius. 81 23

1. Four, six and eight hours after gavage of rats with alpha-mercapto-beta-(2-furan)acrylic acid (MFA) (25 mg/kg) serum zinc concentration was increased ten-fold over control levels and a mean molar ratio of 1 albumin:0-4 zinc:0-8 MFA was found for seventeen sera. 2. At pH 7-5 a maximum of 1 mole of MFA could be bound per mole of metal-free bovine serum albumin. 3. In the presence of zinc ion, albumin-zinc-MFA complexes formed, since for each mole of albumin-zinc complex an additional mole of MFA could be bound to albumin. Complexes up to a molar stoichiometry of 1 albumin:2 zinc:3 MFA were prepared. 4. MFA stabilized the albumin-zinc complex against dissociation. 5. Formation of similar complexes in vivo may account for the markedly delayed clearance of plasma zinc rats administered beta-aryl derivatives of alpha-mercapto-acrylic acid.
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PMID:Formation of a ternary complex with serum albumin: an explanation for the effect of alpha-mercapto-beta-(2-furan) acrylic acid on rat plasma zinc clearance. 88


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