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)

Periodate treatments of apo human serum transferrin (HST), and apo chicken ovotransferrin (COT) were previously reported to cause a rapid loss of Fe+3 binding capacity, with a loss of 3 to 5 tyrosine residues [P. AZARI AND J. L. PHILLIPS (1970) Arch. Biochem. Biophys. 138, 32-38; K. F. GEOGHEGAN, J. L. DALLAS, AND R. E. FEENEY (1980) J. Biol. Chem. 255, 11429-11434]. The effects of periodate and hydrogen peroxide on human lactotransferrin (HLT), HST, and COT have been compared. All three apotransferrins were rapidly inactivated and lost approximately 4 to 5 tyrosine residues by 5 mM periodate treatment; their iron complexes had little or no inactivation and losses of approximately 1 to 2 tyrosine residues. All three iron transferrins were highly resistant to inactivation by 5 mM periodate in bicarbonate, with or without the addition of phosphate, while in phosphate (with ambient carbonate) Fe2HLT was highly resistant, Fe2COT slightly less resistant, and Fe2HST much less resistant. Similar oxidations of methionines to the sulfoxides were found in both the apo and iron forms. After 150 min of 5 mM periodate treatment HST lost approximately 3 (apo 3.1, iron 2.8) of 9, HLT approximately 3 (apo 2.6, iron 2.9) of 6, and COT approximately 7 (apo 7.2, iron 7.2) of 11 methionines per mole of protein. In the presence of 8 M urea HST had essentially all of its methionine residues oxidized by periodate, but only lost part of its activity on renaturation. Treatment of all apo transferrins with 300 mM hydrogen peroxide resulted in little or no losses (less than 10%) in activity. HST lost approximately one-third of its methionines and no tyrosines during the 300 mM hydrogen peroxide treatment. Therefore the essentiality of tyrosines for all three transferrins was confirmed and the nonessentiality of methionines was demonstrated.
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PMID:Comparative oxidations of tyrosines and methionines in transferrins: human serum transferrin, human lactotransferrin, and chicken ovotransferrin. 631 90

Vesicles were prepared from a 9:1 (mole/mol) mixture of dipalmitoyl phosphatidylcholine and the radioactively labeled phospholipids, 1-palmitoyl-2-omega-(m-diazirinophenoxy)undecanoyl-sn-glycero-3-phosphocholine (PC-I) or 1-palmitoyl-2-omega-(2-diazo-3,3,3-trifluropropionyloxy)lauroyl-sn- glycero-3-phosphocholine (PC-II). Rabbit liver cytochrome b5 was inserted into these vesicles spontaneously and the resulting vesicles containing the cytochrome b5 in the transferable form were photolyzed. Cytochrome b5 containing covalently cross-linked phospholipids was isolated by Sephadex LH-60 column chromatography using ethanol/formic acid as the solvent. Of the total radioactivity, 4.6% (PC-I) or 11.3% (PC-II) was linked to the protein; of the former, up to 51% was base-labile, while in the latter, 22% was base-labile. The sites of cross-linking of PC-I to the protein were investigated by fragmentation with trypsin, Staphylococcus aureas V8 protease, CNBr, and o-iodosobenzoic acid followed by Sephadex LH-60 chromatography and Edman sequencing (solid phase) of the appropriate fragments. The distribution of cross-linking was broad (Ser-104 to Met-130), showing a bell-shaped pattern with a significant peak at Ser-118. The labeling pattern is consistent with the previously proposed loop-back model for the membranous segment in the transferable form of cytochrome b5.
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PMID:The membrane-embedded segment of cytochrome b5 as studied by cross-linking with photoactivatable phospholipids. 634 39

The inactivation of soybean lipoxygenase by 5,8,11,14-eicosatetraynoic acid was studied in detail. The inactivation was found to be time-dependent and irreversible. A kinetic scheme, based on the assumption of a rapid inactivation of the enzyme-product complex, yielded a Km value for 5,8,11,14-eicosatetraynoic acid of 1.3 microM, which is about a tenth of that described for arachidonic acid, and a reaction constant k+2 of 0.006s-1, which is four orders of magnitude lower. The reasons for these differences are discussed. Several types of experimental evidence indicate that the first step of the enzyme inactivation is the conversion of 5,8,11,14-eicosatetraynoic acid via a lipoxygenase reaction: (a) the conversion of radioactively labelled methyl ester of 5,8,11,14-eicosatetraynoic acid to other products; (b) the oxygen requirement of the inactivation; (c) the competitive protective effect of linoleic acid; (d) the similarity of the activation energy for both the dioxygenation of linoleic acid and the enzyme inactivation by 5,8,11,14-eicosatetraynoic acid; (e) the formation of one mole methionine sulfoxide/mole enzyme during the reaction with 5,8,11,14-eicosatetraynoic acid, similar to the suicidal reaction of reticulocyte lipoxygenase with 13LS-hydroperoxy-linoleic acid. These results, as well as the lack of covalent binding of 14C-labelled 5,8,11,14-eicosatetraynoic acid methyl ester, contradict the allene mechanism postulated by others [D.T. Downing, D.G. Ahern, and M. Bachta (1970) Biochem. Biophys. Res. Commun. 40, 218-223; K.H. Gibson (1977) Chem. Soc. Rev. 6, 489-510]. It is assumed that the susceptible methionine is located at the active centre of the enzyme.
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PMID:The mechanism of inactivation of lipoxygenases by acetylenic fatty acids. 642 82

The major gamma-carboxyglutamic acid-containing protein of rabbit cortical bone isolated and purified from near-neutral (pH 7.5) EDTA-extracts by DEAE-cellulose and Sephadex G 75 column chromatography had a molecular weight of about 5600 based on integral amino-acid composition; this was confirmed by high-performance liquid chromatography. The purified protein had high glutamic acid and aspartic-acid contents, two to three residues of gamma-carboxyglutamic acid per molecule and zero levels of serine, threonine, methionine, histidine and tryptophan. Equilibrium dialysis indicated that the protein has a weak affinity for calcium ions with a formation constant of 1515 M-1 at I 0.15, pH 7.5, 25 degrees C with a binding capacity of 2 mol calcium per mole protein.
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PMID:The small molecular weight, gamma-carboxyglutamic acid-containing protein of rabbit bone tissue. 659 60

Elastase/elastase inhibitor imbalance in the lung has been implicated in the pathogenesis of pulmonary emphysema. In light of this, it may be significant that the activity of two major elastase inhibitors, alpha 1-proteinase inhibitor (alpha 1-antitrypsin, alpha 1Pi) and bronchial mucous proteinase inhibitor, can be decreased by oxidizing agents. The effect can be observed with ozone, substances present in cigarette smoke, and oxygen metabolites generated by lung macrophages as well as peroxidative systems released by other phagocytic cells. Thus alpha 1Pi recovered from lung washings of cigarette smokers has only half the predicted normal activity per mg inhibitor and contains 4 moles of methionine sulfoxide (oxidized methionine) per mole of inactive inhibitor. By contrast, alpha 1Pi purified from nonsmokers' lung washings is fully active and contains only native methionine. At the same time, lung washes from some smokers show significantly greater hydrolytic activity against a specific synthetic elastase substrate than do lung washes of nonsmokers. These findings suggest that some smokers may develop an acquired imbalance between elastase and elastase inhibitor in their lungs, favoring activity of the enzyme. In addition to the potential effect of cigarette smoking on lung elastase/elastase inhibitor balance, smoking also may interfere with elastin repair mechanisms. Specifically, acidic water-soluble gas phase components of cigarette smoke prevent synthesis of desmosine cross-links during elastinogenesis in vitro. This report will attempt to correlate the foregoing information on biochemical changes in the lung induced by cigarette smoking with the development of emphysema in the smoker.
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PMID:The role of oxidative processes in emphysema. 660 Aug 89

1. The kinetic parameters of lysine and alanine uptake by rabbit ileal mucosa have been measured in the presence and absence of Na. 2. Using lysine as an inhibitor of part of alanine uptake in the absence of Na it has been possible to define two mediated systems for alanine entry. One of these systems (Km 14.2 mM; Jmax 41.3 n-mole cm-2 min-1) is inhibited by lysine (Ki 0.96 mM) while the other (Km 115 mM; Jmax 323 n-mole cm-2 min-1) is not. 3. Methionine is an effective inhibitor of both Na-independent uptake mechanisms for alanine. 4. Na-independent lysine uptake also takes place through two mediated systems. One of these systems (Km 1.0 mM; Jmax 12.8 n-mole cm-2 min-1) is inhibited by alanine (Ki 4.3 mM) while the other (Km 108 mM; Jmax 194 n-mole cm-2 min-1) is not. 5. The use of a naturally occurring basic amino acid to inhibit a portion of neutral amino acid uptake extends considerably the ability to distinguish multiple acid transport systems present in the same cell membrane. The physiological implications of these findings are discussed.
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PMID:Distinguishing transport systems having overlapping specificities for neutral and basic amino acids in the rabbit ileum. 679 99

Adrenal proenkephalin contains the sequence -Asn-Ser-Ser- that is a typical site for the attachment of asparagine-linked carbohydrate. The 5300- and 18,200-Da bovine adrenal proteins derived from proenkephalin contain this recognition sequence and were therefore analyzed for the presence of both amino and neutral sugars. Les than 0.05 mol of amino sugar and less than 0.1 mol of neutral sugar were found per mole of each protein. No amino sugar was detected in other high-molecular-weight adrenal [Met]enkephalin-containing proteins. Together these findings indicate that bovine adrenal proenkephalin does not contain asparagine-linked carbohydrate.
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PMID:Is adrenal proenkephalin glycosylated? 687 Feb 64

1. In the goldfish retina, uptake of exogenous [3H]glycine follows Michaelis--Menten kinetics with increasing concentrations of glycine. This uptake can be explained kinetically by the presence of two independent affinity systems: a 'high-affinity' mechanism with an apparent Km(H) of 8.1 microM and a Vmax(H) of 9.12 p-moles/min. mg protein, and a 'low-affinity' mechanism with an apparent Km(L) of 0.63 mM and a Vmax(L) of 430 p-mole/min . mg protein. 2. The high-affinity mechanism, and probably also the low-affinity mechanism, is temperature- and Na+-dependent. 3. The low-affinity mechanism for glycine uptake is not affected by 5 mM-isoleucine, methionine and valine in the medium. However, it is inhibited more than 90% by 5 mM-alanine, proline and serine in the medium. This result indicates that the low-affinity transport for glycine may go through system A of the neutral amino acid transport system which is present in most tissues to transport glycine and certain neutral amino acids for metabolic purposes. 4. The high-affinity mechanism for glycine uptake is, however, not affected by the presence of up to 100-fold excess of all amino acids examined. 5. Autoradiographic studies show that at least one type of amacrine cell and one type of probable interplexiform cell take up [3H]glycine both in the presence and absence of 5 mM-alanaine, proline and serine, indicating that these neurones possess the high-affinity mechanism for glycine uptake. 6. [3H]Glycine accumulated in the retina can be released by increasing the external K+ concentration. This release is probably Ca2+-dependent since it is blocked by 10 mM-Co2+ in the medium. Additionally, autoradiographic studies show that [3H]glycine taken up by the glycine-accumulating neurones can also be released by Ca2+-dependent, K+-depolarization of the retina.
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PMID:The uptake and release of [3H]glycine in the goldfish retina. 723 15

Total sulfur amino acid (TSAA) requirements and methionine and cystine combinations were investigated during two growth phases (0 to 21 days and 21 to 42 days) of broilers using practical-type diets. For the first growth phase (0 to 21 days), the basal diet contained .62% TSAA to which increasing increments of DL-methionine were added. Both overall growth and feed efficiency improved as methionine levels increased to a level of .82% TSAA. When methionine-cystine combinations were used with the same basal diet, it was found that cystine could supply 54% of the TSAA content. When expressed on a millimolar basis, the methionine requirement was 41%, while cystine could account for 59% of the TSAA's. During the second growth phase (21 to 42 days) a basal diet consisting of .52% TSAA was used along with DL-methionine supplements to determine sulfur amino acid requirements. The trend was towards a slight decrease in requirement from .82% during the first growth period, to between .70% and .76% TSAA in the diet, represented mainly by methionine. When sulfur amino acid combinations were used during this period it appeared the replacement value of cystine for methionine decreased to between 38 and 43% of the TSAA level. Results also suggested that a more efficient way to express the sulfur amino acid requirement may be on a mole per unit of feed basis.
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PMID:Sulfur amino acid requirements and interactions in broilers during two growth periods. 723 65

Phosphoglycerate kinase (EC 2.7.2.3) of Fasciola hepatica was purified 375-fold to homogeneity. The enzyme was monomeric, and had a molecular weight of 47 900 and a sedimentation coefficient of 3.0-3.5 S. The enzyme was composed of 397 amino acids and was relatively rich in sulfur amino acids containing 13 methionine and 2 cysteine residues per mole. The enzyme possessed a highly reactive essential sulfhydryl group and was inhibited irreversibly by iodoacetamide and N-ethylmaleimide and reversibly by p-chloromercuribenzoate and 5,5'-dithio-bis(2-nitrobenzoic acid). Initial velocity studies suggested that reaction occurred via a sequential mechanism. The Km values for 3-phosphoglycerate and ATP were 1.26 and 0.90 mM, respectively. ADP was a noncompetitive inhibitor with respect to both ATP and 3-phosphoglycerate.
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PMID:Purification and characterization of phosphoglycerate kinase from Fasciola hepatica. 724 69


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