Gene/Protein Disease Symptom Drug Enzyme Compound
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 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The stability of oxyhemoglobin S during mechanical shaking was enhanced by the addition of human serum albumin. The stabilizing effect was maximum when the concentration of serum albumin approached that of oxyhemoglobin, suggesting a molecular level interaction between them. The effects of serum albumin on oxyhemoglobin A were essentially similar to those on oxyhemoglobin S. Deoxy- and methemoglobins were also stabilized by serum albumin. The addition of human serum albumin to a solution containing sickle cell oxyhemoglobin slowly formed a compound which had an absorbance peak at 620 nm. After purification by Sephadex G-200 column chromatography, this compound was identified as methemalbumin. Comparison of the rates of formation of methemalbumin from hemoglobin with various ligand states and human serum albumin showed that the rate of formation from hemichrome was much faster than from met-, oxy- and deoxyhemoglobin. About 60% of the heme was transferred from hemichrome to albumin when the mixture was kept standing at room temperature for 5 min, in contrast to only 5% from methemoglobin. This result suggests that hemichrome, rather than methemoglobin, is the intermediate in the formation of methemalbumin from oxyhemoglobin and human serum albumin. This hypothesis is supported by the finding that the rate of formation of methemalbumin was faster at alkaline pH values than at acid pH values. Serum albumin from various animal sources showed different stabilizing effects. The formation of methemalbumin from these animal albumins was far less than that from human albumin.
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PMID:Interaction of serum albumin with normal and sickle hemoglobins. 0 29

Methemoglobin formation was studied at near physiological hemoglobin concentration. The reaction proceeds at a faster rate when the concentration of hemoglobin is high (15-18 mM in heme) than when it is low (2 mM). Constant shaking of hemoglobin preparations during the incubation decreases the differences seen in the rates of autoxidation between concentrated and dilute samples. When red cell hemolysate is used instead of pure hemoglobin, similar results are obtained. A comparison of rates of methemoglobin formation in hemoglobin solutions under low air pressure (1/2 atm) with those under normal air pressure (1 atm) shows no differences between concentrated and dilute samples. There is also no significant difference between the rates of autoxidation of dilute and concentrated solutions when the reactions are carried out under one atmosphere of oxygen (100 percent O2). The study of one patient with hereditary spherocytosis demonstrated higher hemoglobin autoxidation rate in spherocytes, which have higher hemoglobin concentration, than in normal biconcave red cells. These results suggest that: a) the rate of hemoglobin autoxidation at red cell hemoglobin concentration is significantly faster than rates obtained by studying dilute solutions; b) although the accelerated oxidation might be related to multiple factors, one seems to be less accessibility of oxygen when the hemoglobin solution is highly concentrated.
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PMID:Hemoglobin autoxidation at physiological concentrations. 366 22

A study was made of the in vitro stability of hemoglobin-containing liposomes ('hemosomes') prepared from phosphatidylcholines, equimolar cholesterol and red cell lysate by the hand-shaking and ether-injection methods. Absorption spectra indicated hemichrome formation in 'hemosomes' prepared by the ether-injection technique, and increased oxidation of hemoglobin in hand-shaken 'hemosomes'. The denaturation of hemoglobin in ether-injection 'hemoglobin' was increased if the initial methemoglobin content of the hemolysate, or the temperature of preparation was elevated. It was slower if liposomes were prepared under either N2 or CO, or if the radical scavenger 1,3-diphenylisobenzofuran was added with the ether. Egg phosphatidylcholine and synthetic saturated phospholipids gave the same results. With hand-shaken 'hemosomes' the oxidized product was primarily methemoglobin, and oxidation could be inhibited by using saturated phosphatidylcholines instead of egg phosphatidylcholine. Lysophosphatidylcholine levels were higher and arachidonic acid levels lower in egg phosphatidylcholine 'hemosomes' than in equivalent liposomes containing no hemolysate. The 'hemosome' seems to be a suitable model for the study of hemoglobin-lipid membrane interactions and the resulting hemoglobin denaturation process.
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PMID:Oxidation and denaturation of hemoglobin encapsulated in liposomes. 670 23

The molecular stability and function of hemoglobin (Hb) Hasharon (alpha 2 H beta 2) and Hb Hasharon2 (alpha 2 H delta 2) were studied and compared to Hbs A, A2 and S. Hb Hasharon and Hb Hasharon2 had slightly lower P50 values than Hb A and Hb A2 but had normal responses to organic phosphates. The molecular stability of Hb Hasharon and Hb Hasharon2 (as measured by mechanical shaking and heat denaturation at 60 degrees C) were less than Hb A and Hb A2 but greater than Hb S in the oxy- and carbonmonoxy-forms. In the met-form, however, Hb Hasharon and Hb Hasharon2 were less stable than hemoglobins S, A and A2. The oxy-form of Hb Hasharon forms methemoglobin at a faster rate than Hb A and Hb S. The mechanical and heat stabilities and the rate of methemoglobin formation of oxy-Hb Hasharon were studied in the presence of sulfisoxazole. This drug increased the rate of methemoglobin formation, thus causing a further decrease in the stability of Hb Hasharon. The relationship between these laboratory findings and previously observed clinical findings associated with Hb Hasharon are discussed.
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PMID:Molecular stability and function of hemoglobins Hasharon (alpha(2)47 (CD5)Asp----His beta 2) and Hasharon (alpha(2)47 (CD5)Asp----His delta 2). 672 92

1. In the absence of protective agents, highly purified ascorbic acid oxidase is rapidly inactivated during the enzymatic oxidation of ascorbic acid under optimum experimental conditions. This inactivation, called reaction inactivation to distinguish it from the loss in enzyme activity that frequently occurs in diluted solutions of the oxidase prior to the reaction, is indicated by incomplete oxidation of the ascorbic acid as measured by oxygen uptake; i.e., "inactivation totals." 2. A minor portion of the reaction inactivation appears to be due to environmental factors such as rate of shaking of the manometers, pH of the system, substrate concentration, and oxidase concentration. The presence of inert protein (gelatin) in the system ameliorates the environmental inactivation to a considerable extent, and variation of the above factors in the presence of gelatin has much less effect on the inactivation totals than in the absence of gelatin. 3. A major portion of the reaction inactivation of the oxidase appears to be due to some factor inherent in the ascorbic acid-ascorbic acid oxidase-oxygen system, possibly a highly reactive "redox" form of oxygen other than H(2)O(2) or H(2)O. The inactivation cannot be attributed to dehydroascorbic acid, the oxidation product of ascorbic acid. 4. Small amounts of native catalase, native peroxidase, native or denatured methemoglobin, and hemin when added to the system, markedly protect the oxidase against inactivation. Cytochrome c has no such protective action. Likewise proteins such as egg albumin, gelatin, denatured catalase, or denatured peroxidase show no such protective action. 5. None of the protective agents mentioned above affect the initial rate of oxygen uptake or change the total oxygen absorbed for complete oxidation of the ascorbic acid, and hence do not act by removal of hydrogen peroxide, per se. 6. Sodium azide and hydroxylamine hydrochloride which inhibit catalase and peroxidase activity also inhibit the protective action of these iron-porphyrin enzymes.
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PMID:ON THE INACTIVATION OF ASCORBIC ACID OXIDASE. 1987 83