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)

Structure-electron capture sensitivity relationships were established for underivatized 17alpha-acetoxyprogesterones. While progesterone was very insensitive, 17alpha-acetoxyprogesterone had a response of 4.8 X 10(2) C/mole. Methyl groups in the A or B ring of 17alpha-acetoxyprogesterone had no effect. A keto group at C-6 was 25 times more sensitive (1.2 X 10(4) C/mole). A double bond at C-6,7 enhanced the sensitivity sevenfold (3.5 X 10(3) C/mole), but double bonds at C-1,2 or C-9,11 had only slight effect. Substitution at C-16 was important. A methyl group at C-16 had two and three times the sensitivity in the 3-keto delta4 and 3-keto delta4,6 series (1.1 X 10(3) and 1.1 X 10(4) C/mole), respectively. A methylene group at C-16, in contrast showed a six-and twofold greater sensitivity over the C-16 methyl in the two series (7 X 10(3) and 2.2 X 10(4) C/mole), respectively. The most sensitive compound was 6-dehydro-6methyl-16-methylene-17alpha-acetoxyprogesterone (melengestrol acetate). Its sensitivity was 2.2 X 10(4) C/MOL, Comparable to the most sensitive halo esters of steroid alcohols reported in the literature. Its electron capture coefficient was 3-7.6X 10(10) 1/mole. The coef-icient was independent of the detector temperature, indicating low activation energy for electron absorpiton.
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PMID:Structure-gas chromatographic electron capture sensitivity relationships of some substituted 17alpha-acetoxyprogesterones. 97

A simple method was developed to produce 14C-labeled aflatoxin B1 by using the yeastlike phase of Aspergillus parasiticus NRRL 2999. Yeastlike cultures resulted from absence of manganese in a synthetic medium. Sodium acetate-1-14C had a 0.22% average incorporation; sodium acetate-1,2-14C, 0.70%. The average yield of labeled B1 was 10 mg/500 ml medium with an average specific activity of either 63.3 mCi/mole (C-1 label) or 194.3 mCi/mole (C-1, 2 label).
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PMID:14C-Labeled aflatoxin B1 prepared with yeastlike cultures of Aspergillus parasiticus. 100 52

The carbon dioxide solubility coefficient, alphaCO2, and the apparent carbonic acid dissociation constants, K'1 and K'2 were estimated in the serum of the crab Carcinus maenas at various temperatures and ionic strengths. At 15 degrees C, the indirectly determined alphaCO2 value is 0-0499 m-mole l-1 torr-1 for crabs living in normal sea water (salinity ca. 35 percent). It is apparently independent of the serum protein concentration and of the stage of the moulting cycle. For crabs living in undiluted sea water, the mean pK'1 value, determined either gasometrically or titrimetrically, is 6-027 at 15 degrees C. At the same temperature, pK'2=9-29. These values approximate to those of sea water at 35 percent salinity. pK'1 drops as temperature rises; the measured deltapK'1/deltat is -0-0053 pH unit degrees C-1 between 10 and 30 degrees C. PK'1 rises as the ionic strength is lowered. Alignment nomograms have been constructed for the determination of alphaCO2, pK'1 and pK'2 values in relation to various conditions of temperature and salinity.
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PMID:Carbon dioxide combining properties of the blood of the shore crab Carcinus maenas (L): carbon dioxide solubility coefficient and carbonic acid dissociation constants. 127 Sep 94

1. The production rate of propionate in the rumen and the entry rate of glucose into the body pool of glucose in sheep were measured by isotope-dilution methods. Propionate production rates were measured by using a continuous infusion of specifically labelled [(14)C]propionate. Glucose entry rates were estimated by using either a primed infusion or a continuous infusion of [U-(14)C]glucose. 2. The specific radioactivity of plasma glucose was constant between 4 and 9hr. after the commencement of intravenous infusion of [U-(14)C]glucose and between 1 and 3hr. when a primed infusion was used. 3. Infusion of [(14)C]propionate intraruminally resulted in a fairly constant specific radioactivity of rumen propionate between about 4 and 9hr. and of plasma glucose between 6 and 9hr. after the commencement of the infusion. Comparison of the mean specific radioactivities of glucose and propionate during these periods allowed estimates to be made of the contribution of propionate to glucose synthesis. 4. Comparisons of the specific radioactivities of plasma glucose and rumen propionate during intraruminal infusions of one of [1-(14)C]-, [2-(14)C]-, [3-(14)C]- and [U-(14)C]-propionate indicated considerable exchange of C-1 of propionate on conversion into glucose. The incorporation of C-2 and C-3 of propionate into glucose and lactate indicated that 54% of both the glucose and lactate synthesized arose from propionate carbon. 5. No differences were found for glucose entry rates measured either by a primed infusion or by a continuous infusion. The mean entry rate (+/-s.e.m.) of glucose estimated by using a continuous infusion into sheep was 0.33+/-0.03 (4) m-mole/min. and by using a primed infusion was 0.32+/-0.01 (4) m-mole/min. The mean propionate production rate was 1.24+/-0.03 (8) m-moles/min. The conversion of propionate into glucose was 0.36 m-mole/min., indicating that 32% of the propionate produced in the rumen is used for glucose synthesis. 6. It was indicated that a considerable amount of the propionate converted into glucose was first converted into lactate.
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PMID:Contribution of propionate to glucose synthesis in sheep. 486 May 45

Anaerobic reduction of purified rabbit IgG antibody (Ab) with 1.5 moles of dithiothreitol per mole of Ab at pH 8.0, followed by alkylation, cleaves 39% of the inter-heavy-chain (H-H) disulfide (SS) bonds. This treatment has the following effects on the ability of the Ab to activate the classical pathway of complement. Compared to control Ab, reduced and alkylated (RA) Ab retained 4-5.6% of overall hemolytic activity and 55% of complement-fixing activity at 0 degrees C. Complexes of RA Ab and equivalent amounts of soluble Ag consumed C4, C2 and C3 at 37, 51 and 44%, respectively, of the rate at which these components were consumed by equal concns of complexes containing control Ab. Complexes made with RA Ab bound 18% as much C-1 as those made with native Ab. These data indicate that the principal, if not the only, effect of RA is on C-1 binding. Measurements of the ability of complexes of Ab with cell-bound Ag to bind C-1 showed at most a 20% loss of C-1 binding sites and a ca two-fold decrease in affinity for C-1. Similar results were obtained with purified (activated) C-1 and with native C1 in serum. No significant difference could be detected in the rate of activation of bound C1. Normal rabbit IgG which was reduced and alkylated under the same conditions retained 52% of its H-H SS bonds and 30% of its ability to bind C-1. This finding suggests that the impairment in C-1 binding results from an effect on the C1 binding site itself, rather than from an effect on the ability of the RA Ab to transmit a putative conformational "signal" from the Ag-binding site to the C1 binding site. Finally, our data show that the observed functional effect of reduction and alkylation depends strongly on the assay used to evaluate that effect.
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PMID:Effect of reduction and alkylation on structure and function of rabbit IgG antibody--II. Effects on classical pathway C3 convertase formation. 656 90

We examined the unitrophic metabolism of acetate and methanol individually and the mixotrophic utilization of these compounds by using detailed (14)C-labeled tracer studies in a strain of Methanosarcina barkeri adapted to grow on acetate as the sole carbon and energy source. The substrate consumption rate and methane production rate were significantly lower on acetate alone than during the unitrophic or mixotrophic metabolism of methanol. Cell yields (in grams per mole of substrate) were identical during exponential growth on acetate and exponential growth on methanol. During unitrophic metabolism of acetate, the methyl moiety accounted for the majority of the CH(4) produced, but 14% of the CO(2) generated originated from the methyl moiety. This correlated with the concurrent reduction of equivalent amounts of the C-1 of acetate to CH(4). (14)CH(4) was also produced from added (14)CO(2), although to a lesser extent than from reduction of the C-1 of acetate. During mixotrophic metabolism, methanol and acetate were catabolized simultaneously. The rates of (14)CH(4) and (14)CO(2) generation from [2-(14)C]acetate were logarithmic and higher in mixotrophic than in unitrophic cultures at substrate concentrations of 50 mM. A comparison of the oxidoreductase activities in cell extracts of the acetate-adapted strain grown on acetate and of strain MS grown on methanol or on H(2) plus CO(2) indicated that the pyruvate, alpha-ketoglutarate, and isocitrate dehydrogenase activities remained constant, whereas the CO dehydrogenase activity was significantly higher (5,000 nmol/min per mg of protein) in the acetate-adapted strain. These results suggested that a significant intramolecular redox pathway is possible for the generation of CH(4) from acetate, that energy metabolism from acetate by M. barkeri is not catabolite repressed by methanol, and that the acetate-adapted strain is a metabolic mutant with derepressed CO dehydrogenase activity.
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PMID:Comparison of unitrophic and mixotrophic substrate metabolism by acetate-adapted strain of Methanosarcina barkeri. 679 21

A peptidylarginine deiminase (PAD; EC 3.5.3.15) has been isolated from bovine brain and some of its characteristics have been studied. The enzyme showed an absolute requirement for Ca2+, a temperature optimum at approximately 50 degrees C, and two Km values when benzoylarginine ethyl ester was used as substrate, 0.78 mM and 11.2 mM. The higher Km has not been reported previously. Protein substrates for the enzyme included polyarginine and myelin basic protein but not histones. Because one of the components of MBP contains six citrullinyl residues per mole, enzymic deimination appeared to be a likely mechanism. When the most cationic component (C-1) was subjected to PAD in solution, 17 of the 19 arginyl residues were modified. From sequence analyses we concluded that the nature of the amino acid residues adjacent to the deiminated arginine were not modifiers of the reaction as arginyl residues in a variety of environments were deiminated. This deimination was reflected in a large increase in random structure, as measured by [theta]200. At 5 degrees C, the [theta]200 of the deiminated protein was -70 x 10(3) compared with -30 x 10(3) deg.cm2/dmol for the native protein. When the temperature was increased to 70 degrees C, the [theta]200 was -44 x 10(3) for the deiminated protein and -20 x 10(7) deg.cm2/dmol for the native C-1. When plotted as a function of temperature, [theta]200 decreased linearly from 5 degrees C to 50 degrees C for both proteins and did not change from 50 degrees C to 70 degrees C. PAD provides a mechanism for deimination of arginyl residues of myelin basic protein. The selective deimination of the six arginyl residues that are consistently found deiminated in C-8 may be determined by the orientation of the protein in the membrane and/or the more complex lipid composition of myelin may affect the selectivity of the deimination.
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PMID:Deimination of human myelin basic protein by a peptidylarginine deiminase from bovine brain. 768 46

Body temperature, oxygen consumption, respiratory and cardiac activity and body mass loss were measured in six females and four males of the subterranean Zambian mole rat Cryptomys sp. (karyotype 2 n = 68), at ambient temperatures between 10 and 35 degrees C. Mean body temperature ranged between 36.1 and 33.2 degrees C at ambient temperatures of 32.5-10 degrees C and was lower in females (32.7 degrees C) than in males (33.9 degrees C) at ambient temperatures of 10 degrees C but did not differ at thermoneutrality (32.5 degrees C). Except for body temperature, mean values of all other parameters were lowest at thermoneutrality. Mean basal oxygen consumption of 0.76 ml O2.g-1.h-1 was significantly lower than expected according to allometric equations and was different in the two sexes (females: 0.82 ml O2.g-1.h-1, males: 0.68 ml O2.g1.h-1) but was not correlated with body mass within the sexes. Basal respiratory rate of 74.min-1 (females: 66.min1, males: 87.min-1) and basal heart rate of 200.min-1 (females: 190.min-1, males: 216.min-1) were almost 30% lower than predicted, and the calculated thermal conductance of 0.144 ml O2.g-1.h1.degrees C-1 (females: 0.153 ml O2.g-1.h-1.degrees C-1, males: 0.131 ml O2.g-1.h-1.degrees C-1) was significantly higher than expected. The body mass loss in resting mole rats of 8.6-14.1%.day-1 was high and in percentages higher in females than in males. Oxygen consumption and body mass loss as well as respiratory and cardiac activity increased at higher and lower than thermoneutral temperatures. The regulatory increase in O2 demand below thermoneutrality was mainly saturated by increasing tidal volume but at ambient temperatures < or = 15 degrees C, the additional oxygen consumption was regulated by increasing frequency with slightly decreasing tidal volume. Likewise, the additional blood transport capacity was mainly effected by an increasing stroke volume while there was only a slight increase of heart frequency. In an additional field study, temperatures and humidity in different burrow systems have been determined and compared to environmental conditions above ground. Constant temperatures in the nest area 70 cm below ground between 26 and 28 degrees C facilitate low resting metabolic rates, and high relative humidity minimizes evaporative water loss but both cause thermoregulatory problems such as overheating while digging. In 13-16 cm deep foraging tunnels, temperature fluctuations were higher following the above ground fluctuations with a time lag.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The energetics of the common mole rat Cryptomys, a subterranean eusocial rodent from Zambia. 773 32

The structures of novel antimicrobial antibiotics, amythiamicins A, B and C, were elucidated by chemical degradations and NMR spectral analyses. The main frame from C-1 to C-41 of these antibiotics was the same as that of amythiamicin D. Amino acid autoanalyses of amythiamicins A, B and C showed that these have another one mole of serine and proline in comparison with amythiamicin D. Stereochemistries of both amino acids were determined to be L by chiral HPLC. These seryl-prolyl residues in amythiamicins A, B and C are attached at C-41 through an oxazoline ring, amide and ester bond, respectively.
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PMID:Novel antibiotics, amythiamicins. III. Structure elucidations of amythiamicins A, B and C. 796 Nov 66

The catalytic amino acid residue of Aspergillus niger alpha-glucosidase (ANGase) was identified by modification with conduritol B epoxide (CBE), a mechanism-based irreversible inactivator. The inactivation by CBE followed pseudo-first order kinetics. The interaction of CBE and ANGase conformed to a model with a reversible enzyme-inhibitor complex formed before covalent inactivation. A competitive inhibitor, Tris, decreased the inactivation rate. The incorporation of one mole of CBE per mole of ANGase was completely abolished the enzyme activity. A dissociated carboxyl group (-COO-) in the active site was suggested to attack the C-1 of CBE. ANGase was composed of two subunits (P1 and P2), of which P2 was modified by CBE. The labelled residue was included in a peptide (LY3) that was obtained from Lys-C protease digestion of CBE-bound P2. The sequence analysis of CBE-labelled LY3 showed that an Asp was the modified residue, that is, one of the catalytic amino acid residues of ANGase. The primary structure of LY3 was determined by analyzing the sequence of peptide fragments prepared by several proteases.
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PMID:A catalytic amino acid and primary structure of active site in Aspergillus niger alpha-glucosidase. 925 70


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