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)

The extrinsic 33-kDa protein (P33) was cross-linked covalently to the binding site on P33-depleted PSII preparations which is responsible for reconstitution of photosynthetic water oxidation after PSII preparations have been washed with 1 M CaCl2. Conditions were found in which more than half of the cross-linked protein complexes formed in the PSII preparations retained the ability to catalyze the oxidation of water. The complex is composed of the P33 cross-linked to the D1 and D2 proteins and a 34-kDa protein, which is present in lower abundance than the other three proteins. After solubilization of the membranes with SDS and purification by preparative SDS-PAGE, the complex retains bound manganese and can catalyze the conversion of H2O2 to O2. Calcium and chloride increased the catalase activity of the purified cross-linked complex while lanthanum or hydroxylamine abolished the activity. By use of the specific activity of the H2O2-dependent reaction to follow the extent of purification of the cross-linked complex, the most highly purified complex was determined to contain 0.34 microgram of manganese/180 micrograms of protein. The mole ratio of Mn/protein was calculated to range from 3.6 to 4.5 depending on the assumed stoichiometry of the protein subunits. The results presented here provide direct evidence that one or more of the three proteins that have cross-linked to the P33 are responsible for binding the manganese of the oxygen-evolving complex.
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PMID:Manganese-binding proteins of the oxygen-evolving complex. 267 50

We have studied the influence of the antilipidemia drug, clofibrate, and several structurally related analogs on the binding affinity of hemoglobin for oxygen and the radiation sensitivity of the SCCVII/St carcinoma in the mouse. Several compounds in this class reduced hemoglobin affinity in vivo; and two of these, ML1024 (etophyline clofibrate) and ML1037, were at least as effective as clofibrate at reducing hemoglobin affinity and much less toxic. When given orally at a dose of 4.1 m mole/Kg, 1/2-2 hrs before 20 Gy X rays, clofibrate gave radiosensitization in the SCCVII/St tumor equivalent to a 40-fold reduction in hypoxic fraction. ML1024 and ML1037 at a dose (3.0 m mole/Kg), which had a similar effect on hemoglobin, gave much less sensitization of the tumor. Only ML1024 produced a statistically significant effect, equivalent to a four-fold reduction in hypoxic fraction. We conclude that there are several clofibrate analogs which in relation to their toxicity are much better hemoglobin modifiers than the parent compound. They do not, however, show the same radiosensitizing effects, leading us to believe that mechanisms other than changes in hemoglobin/oxygen binding must also be involved.
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PMID:Chlorophenoxy acetic acid derivatives as hemoglobin modifiers and tumor radiosensitizers. 271 68

In erythropoietic protoporphyria and lead poisoning, free protoporphyrin (PPIX) and zinc protoporphyrin (ZPP), respectively, accumulate in erythrocytes. That PPIX and ZPP bind to human hemoglobin A (Hb4) is established, but the site of binding is still a matter of controversy. We investigated the interaction of ZPP with intact, tetrameric oxy Hb4, using batch microcalorimetry, front-face fluorometry, absorption difference spectroscopy, oxygen equilibrium studies, and isoelectric focusing (IEF). In the presence of oxy Hb4 (pH 7.35, 0.05 M phosphate), the fluorescence emission maximum (excitation at 420 nm) of ZPP immediately shifts from 587 nm (ZPP alone) to 594 nm, as expected when binding to protein. The fluorescence intensity increases with time and is correlated with the ZPP:Hb4 mole ratio. A slow, time-dependent reaction is also observed with microcalorimetry: the rate of heat of reaction exhibits both a fast and a slow component. The heats of reaction range from -2.1 to -14.8 mcal depending upon the ZPP:Hb4 ratio of 4:1 (0.4 mM:0.1 mM) to 38:1 (3.8 mM:0.1 mM), respectively, and are typical of weak, noncovalent protein-ligand interactions. The optical difference spectra are a function of the ZPP:Hb4 molar ratio and also exhibit a slow increase in intensity over time. No time-dependent optical difference spectra are observed with ZPP or with Hb4 alone. The oxygen affinity of Hb4 in the presence of ZPP decreases with increasing mole ratio. During IEF, all ZPP separates from Hb4, consistent with a weak, noncovalent interaction at a non-heme pocket site. We conclude that ZPP binds to intact, tetrameric hemoglobin at non-heme pocket sites in a nonspecific, weak, noncovalent interaction.
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PMID:Interaction of zinc protoporphyrin with intact oxyhemoglobin. 271 38

In the presence of phenylalanine and molecular oxygen, activated phenylalanine hydroxylase catalyzes the oxidation of tetrahydrobiopterin. The oxidation of this tetrahydropterin cofactor also proceeds if the substrate, phenylalanine, is replaced by its product, tyrosine, in the initial reaction mixture. These two reactions have been defined as coupled and uncoupled, respectively, because in the former reaction 1 mol of phenylalanine is hydroxylated for every mole of tetrahydrobiopterin oxidized, whereas in the latter reaction there is no net hydroxylation of tyrosine during the oxidation of the tetrahydropterin. During the course of the coupled oxidation of tetrahydrobiopterin, a pterin 4a-carbinolamine intermediate can be detected by ultraviolet spectroscopy (Kaufman, S. (1976) in Iron and Copper Proteins (Yasunobu, K. T., Mower, H. F., and Hayaishi, O., eds) pp. 91-102, Plenum Publishing Corp., New York). Dix and Benkovic (Dix, T. A., and Benkovic, S. J. (1985) Biochemistry 24, 5839-5846) have postulated that the formation of this intermediate only occurs when the oxidation of the tetrahydropteridine is tightly coupled to the concomitant hydroxylation of the aromatic amino acid. However, during the tyrosine-dependent uncoupled oxidation of tetrahydrobiopterin by phenylalanine hydroxylase, we have detected the formation of a spectral intermediate with ultraviolet absorbance that is essentially identical to that of the carbinolamine. Furthermore, this absorbance can be eliminated by the addition of 4a-carbinolamine dehydratase, an enzyme which catalyzes the dehydration of the 4a-carbinolamine. Quantitation of this intermediate suggests that there are two pathways for the tyrosine-dependent uncoupled oxidation of tetrahydrobiopterin by phenylalanine hydroxylase because only about 0.3 mol of the intermediate is formed per mol of the cofactor oxidized.
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PMID:Evidence for the formation of the 4a-carbinolamine during the tyrosine-dependent oxidation of tetrahydrobiopterin by rat liver phenylalanine hydroxylase. 272 90

Rhodamine G was found to activate blood plasma chemiluminescence induced by ferrous ions. The dye in concentrations 300-500 mole/l increased chemiluminescence by an order of magnitude. The luminescence was inhibited by histidine and SOD. A conclusion may be drawn that the mechanism of the activated ferrous chemiluminescence with rhodamine G was related to superoxide anion-radicals and singlet oxygen.
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PMID:[Chemiluminescence activated by rhodamine G in plasma in the presence of divalent iron ions]. 280 56

A case of hemihypertrophy associated with multiple anomalies of the skin, bone and visceral organs is presented. A 31-year-old female was admitted for evaluation of her skin conditions. Her family history is noncontributory, while her past history discloses operations for syndactyly of the right foot, tonsillar hypertrophy, anal prolapse and ovarial cyst. Erythemas of the face and the left upper extremity were noticed during the neonatal period and hypertrophy of the right side of the body started at age 2 months. On admission, hemihypertrophy was observed in the face, trunk and extremities. Multiple faint nevi flammei were seen on the right half of the face and on the left side of the trunk and extremities. Telangiectasis and nevus anemicus were seen in the upper chest. The left upper extremity showed diffuse brown patches that was histologically basal pigmentation with some giant melanosomes. Visceral anomalies consisted of fibromatous tumors of the tip of the tongue and mitral prolapse. Angiography and computed tomography revealed a possible arteriovenous malformation of the right occipital region, small hemangiomas around the patella, dilation of the lateral ventricle, and calcification of the choroid plexus. Tortuous superficial veins were noted in the right leg. She had no seizure, but her IQ was 68. The bone disorders consisted of scoliosis, short forth metacarpus, hypoplastic mandible and peroneal exostosis. Examination revealed a slight diminution of urinary corticosteroid, but no other endocrinological disorders were found. The hemihypertrophy in this case is at least partially due to an arteriovenous shunt, suggested by elevated oxygen saturation of the blood obtained from the internal saphenous vein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Congenital hemihypertrophy associated with cutaneous pigmento-vascular, cerebral, visceral and bone abnormalities]. 282 Feb 92

Differential oxygen binding measurements obtained over the pH range 6.95 to 9.10 at 25 degrees C have allowed a detailed description of the alkaline Bohr effect of human hemoglobin Ao. Phenomenological analysis of the data in terms of the Adair equation shows that: (1) the oxygen binding curves are asymmetrical with the population of the triply oxygenated species being negligible throughout the pH range studied: (2) the shape of the oxygen binding curve is affected by pH, especially at low saturation; and (3) the maximum O2-proton linkage is -0.52 mole of proton per mole of oxygen at pH 7.4. A possible molecular mechanism of the Bohr effect is proposed within the framework of an allosteric model which accounts for the low population of triply oxygenated hemoglobin species. At least three Bohr groups are necessary for a quantitative description of the alkaline Bohr effect. Two of these groups titrate in the range of the His146 beta and Vall alpha residues, which have long been identified as the main alkaline Bohr groups, and altogether contribute 84% of the alkaline Bohr effect at physiological pH. A third ionizable group, linked to oxygenation presumably at the beta chains, is implicated and is titrated in a pH range characteristic of a surface histidyl residue.
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PMID:Alkaline Bohr effect of human hemoglobin Ao. 284 May 10

Monoamine oxidase (MAO) activity was measured in ring dove (Streptopelia risoria) tissues using a fluorometric assay with kynuramine as substrate. Harmaline inhibited MAO activity in a time-dependent manner, and preincubation of enzyme with the drug did not affect its activity. Pargyline produced a slow-onsetting inhibition of activity which was enhanced by preincubation of enzyme and inhibitor. Harmaline displayed reversible non-competitive inhibition of MAO activity. Oxygen is also a substrate for dove MAO, and the reaction apparently involves "ping-pong", double-displacement kinetics. Dove MAO activity is temperature-dependent, with an activation energy of 13.1 kcal/mole.
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PMID:Biochemistry and physiology of monoamine oxidase (MAO) activity in the ring dove (Streptopelia risoria). I. Characteristics of MAO activity in vitro. 286 15

When the heat-activated chloroplast F1 ATPase hydrolyzes [3H, gamma-32P]ATP, followed by the removal of medium ATP, ADP, and Pi, the enzyme has labeled ATP, ADP, and Pi bound to it in about equal amounts. The total of the bound [3H]ADP and [3H]ATP approaches 1 mol/mol of enzyme. Over a 30-min period, most of the bound [32P]Pi falls off, and the bound [3H]ATP is converted to bound [3H]ADP. Enzyme with such remaining tightly bound ADP will form bound ATP from relatively high concentrations of medium Pi with either Mg2+ or Ca2+ present. The tightly bound ADP is thus at a site that retains a catalytic capacity for slow single-site ATP hydrolysis (or synthesis) and is likely the site that participates in cooperative rapid net ATP hydrolysis. During hydrolysis of 50 microM [3H]ATP in the presence of either Mg2+ or Ca2+, the enzyme has a steady-state level of about one bound [3H]ADP per mole of enzyme. Because bound [3H]ATP is also present, the [3H]ADP is regarded as being present on two cooperating catalytic sites. The formation and levels of bound ATP, ADP, and Pi show that reversal of bound ATP hydrolysis can occur with either Ca2+ or Mg2+ present. They do not reveal why no phosphate oxygen exchange accompanies cleavage of low ATP concentrations with Ca2+ in contrast to Mg2+ with the heat-activated enzyme. Phosphate oxygen exchange does occur with either Mg2+ or Ca2+ present when low ATP concentrations are hydrolyzed with the octyl glucoside activated ATPase. Ligand binding properties of Ca2+ at the catalytic site rather than lack of reversible cleavage of bound ATP may underlie lack of oxygen exchange under some conditions.
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PMID:Bound adenosine 5'-triphosphate formation, bound adenosine 5'-diphosphate and inorganic phosphate retention, and inorganic phosphate oxygen exchange by chloroplast adenosinetriphosphatase in the presence of Ca2+ or Mg2+. 287 34

When perfused cortex-free ox adrenal medulla was stimulated to secrete catecholamine by infusion of 0.1 mM acetylcholine for 4 min, the oxygen consumption increased to a value which was 0.15 +/- 0.07 mumole O2/min/g wet weight (+/- S.D., N = 12) above the pre-stimulation value of 0.49 +/- 0.15 (P less than 0.001). 1.4 +/- 0.9 (+/- S.D., N = 12) mole of catecholamine was secreted per mole of enhanced O2 consumption in the 16 min following the start of the stimulation. The rate of ATP hydrolysis by the proton-translocating Mg-ATPase of the chromaffin granule may increase on fusing with the plasma membrane of the chromaffin cell during exocytosis. However, from the amount of catecholamine secreted, this was estimated to account for less than 17% of the oxygen consumption increase. The amount of catecholamine secreted by 4 min 0.1 mM acetylcholine stimulations correlated with the enhancement of oxygen consumption (r = 0.82, P less than 0.001) but, on stimulation with 60 microM veratridine for 4 min, O2 consumption enhancement was anomalously low. This dependence on mode of stimulation suggests that ATP consumption in exocytosis itself is an inadequate explanation. Ouabain-sensitive oxygen consumption rose from undetectable levels to 18 +/- 8% (+/- S.D., N = 4) of the basal respiration during prolonged 0.1 mM acetylcholine stimulation in the absence of Ca, indicating that Na,K-ATPase was not responsible for all of the oxygen consumption enhancement.
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PMID:Enhanced oxygen consumption in adrenal medulla on stimulation with acetylcholine. 298 35


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