Function and importance of glutamate for savory foods.
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Flavoring systems are of vital importance in savory food manufacturing. Many industrially prepared foods are particularly attractive to potential consumers primarily because of their typical flavors. Therefore, it is no surprise that the food industry dealing with these product segments shows great interest in the use of food or food ingredients carrying the typical umami taste and flavor enhancement systems. Figures are provided showing the importance of glutamate in traditional cuisines and also in meals prepared by industrial manufacturing. It is also interesting to see how food intake patterns of glutamate differ from one cultural group to another. The ever-growing importance of balanced food formulations (carbohydrates, fats, proteins and minerals) brings special challenges to the use of different ingredients, requiring development of appropriate flavor delivery systems. Again flavor enhancement is of great importance. Questions about the addition of glutamate or the total glutamate content of foods are of little importance, from a scientific point of view. However, in a given legal framework, important business opportunities can be realized. One of the main concerns of manufacturers of savory food is how to provide the consumer with tasty foods while complying with increasingly severe local legal constraints concerning the use of many potent flavoring systems. (+info)
Adducts between the carcinogen 2-acetamidophenanthrene and adenine and guanine of DNA.
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The sulfate and acetate esters of the carcinogen N-hydroxy-2-acetamidophenanthrene attack calf thymus DNA in vitro to yield adducts of 2-acetamidophenanthrene with guanine and adenine in the DNA. These adducts were found to be 8-(N-2-phenanthrylacetamido)deoxyguanosine and N6-1-(2-acetamidophenanthryl)deoxyadenosine, respectively. These reactions, and the already known reactions of esters of N-hydroxy-2-acetamidofluorene, together with Huckel molecular orbital calculations, suggest that the relative tendencies of a series of N-aryl-N-acetylnitrenium ions to react with adenine and guanine may be predicted. (+info)
Preparation and antibacterial activity upon Micrococcus luteus of derivatives of iturin A, mycosubtilin and bacillomycin L, antibiotics from Bacillus subtilis.
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Methylated and acetylated derivatives of iturin A and mycosubtilin and methylated derivatives of bacillomycin L were prepared and their antibacterial activity on Micrococcus luteus was compared with the activity of the original substance. the results obtained show the importance of polar groups for the antibiotic activity of the substances of iturin group. (+info)
New high-molecular decomposition products of natamycin (pimaricin) with intact lactone-ring.
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Mild acid treatment of natamycin (IV) results in biologically inactive aponatamycin (VI), an amphoteric substance with some natamycin-like chemical and physical properties. Aponatamycin contains one natamycin- and one natamycinolide-moiety. More drastic acid degradation of natamycin eliminates the aminosugar under formation of the dimer (VII) of the hypothetical aglycone of natamycin, natamycinolide (V) as well as a non-ionic compound, the dimer of the 12-decarboxy-11-anhydro analogue of natamycinolide. (+info)
Studies on human antihemophilic factor. Evidence for a covalently linked subunit structure.
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When purified antihemophilic factor (Factor VIII) was rechromatographed on 4% agarose in 0.15 M NaCl or 1.0 M NaCl, a single protein peak, containing both procoagulant activity and von Willebrand factor activity, as defined by ristocetin-induced platelet aggregation, was eluted in the void volume. Purified Factor VIII immediately lost about 30% of its procoagulant activity when dissolved in 0.25 M CaCl2, and when rechromatographed on 4% agarose in 0.25 M CaCl2, the protein peak and von Willebrand factor activity remained coincident in the void volume; however, most of the remaining procoagulant activity was eluted after the void volume. The elution position of Factor VIII procoagulant activity from 4% agarose in 0.25 M CaCl2, and hence its apparent molecular weight, varied with the protein concentration applied to the column; at low protein concentrations it was eluted close to the inner volume. Yet on Sephadex G-200 in 0.25 M CaCl2, the protein and procoagulant activity were eluted together in the void volume. These observations suggested that the Factor VIII procoagulant activity was not eluting according to size or shape, but was adsorbing to some extent to the agarose. Isolated activity peak material from the 0.25 M CaCl2 columns contained protein and had a typical ultraviolet spectrum. Even at high concentrations, the protein contained no thrombin, Factors IX, X, or Xa activity, or detectable phospholipid. In addition to Factor VIII procoagulant activity, which could be inactivated by a human antibody to Factor VIII, the activity peak protein also contained von Willebrand factor activity. Like native Factor VIII and the void volume protein, the activity peak contained protein that did not enter a sodium dodecyl sulfate 5% polyacrylamide gel in the absence of reducing reagent. After reduction of disulfide bonds, several subunits ranging from 195,000 to 30,000 daltons were observed. These results indicate that the protein in the shifted Factor VIII procoagulant activity peak is large and that its anomalous elution pattern from 4% agarose in 0.25 M CaCl2 results from interaction with the agarose. The Factor VIII-like properties of the activity peak protein and its electrophoretic pattern on sodium dodecyl sulfate gels suggest that it is a species of Factor VIII modified by proteolytic cleavage. These results allow an interpretation that is different from the recently proposed "carrier protein-small active subunit" hypotheses for the structure-function relationships of the Factor VIII molecule. (+info)
The asymmetric distribution of enzymic activity between the six subunits of bovine liver glutamate dehydrogenase. Use of D- and L-glutamyl alpha-chloromethyl ketones (4-amino-6-chloro-5-oxohexanoic acid.
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A method for the preparation of D- and L-glutamyl alpha-chloromethyl ketones (4-amino-6-chloro-5-oxohexanoic acid) is described. These chloromethyl ketones irreversibly inactivated bovine glutamate dehydrogenase, whereas several other related compounds had no adverse effect on the activity of the enzyme. The inactivation process was shown to be due to the modification of lysine-126. The time-courses for the inactivation and the incorporation of radioactivity from tritiated L-glutamyl alpha-chloromethyl ketone into the glutamate dehydrogenase were biphasic. The results were interpreted to suggest the involvement of 'negative co-operative' interactions in the reactivity of lysine-126. From the cumulative evidence it is argued that the first subunit of the enzyme, which takes part in catalysis, makes the largest, and the last the smallest, contribution to the overall catalysis. It is emphasized that three of the six subunits of the enzyme may possess as much as 80% of the total activity of bovine glutamate dehydrogenase. (+info)
Demonstration of two functionally heterogenous groups within the activities of UDP-glucuronosyltransferase towards a series of 4-alkyl-substituted phenols.
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1. A simple colorimetric assay for UDP-glucuronosyltransferase activities towards phenolic substrates, using Folin & Ciocalteu's phenol reagent, is described. The assay is used to measure rat liver transferase activities towards substrates from a series of 4-alkyl-substituted phenols. 2. Activities towards phenol, 4-methylphenol and 4-ethylphenol develop near-adult values before birth, are precociously stimulated by dexa methasone in utero and are stimulated 3--4-fold by 3-methylcholanthrene in adult liver. These are assigned to a "late-foetal" group of transferase activities. 3. Activities towards 4-n-propylphenol, 4-s-butylphenol and 4-t-butylphenol are negligible in late-foetal liver, developing to near-adult values in the first 4 postnatal days, and are not affected by dexamethasone or 3-methylcholanthrene. They are assigned to a "neonatal" group of transferase activities. 4. Although 4-ethylphenol and 4-n-propylphenol differ only by a single --CH2-- moiety, this is sufficient to change the acceptability of these substrates respectively from the late-foetal to the neonatal group of transferase activities. The change is distinct, with no overlapping of substrate acceptability between the two groups of transferase activities. 5. From consideration of the above and other substrates, the two groups of transferase activities do not distinguish substrates on the basis of their molecular weights or lipophilicity. The distinguishing feature appears to be the specific molecular configurations of the substrates. (+info)
Effect of lipophilicity of nitroimidazoles on radiosensitization of hypoxic bacterial cells in vitro.
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The effect of radiosensitization of hypoxic bacterial cells by 9 nitroimidazoles was measured in the bacterial strains E. coli AB 1157 and S. lactis 712. Seven of these compounds were similar to misonidazole in their redox properties, but differed widely in their lipophilicites. The dependence of sensitization enhancement on reduction potential was similar to that reported in mammalian cells. The efficiency of sensitization was similar for compounds of low lipophilicity, but increased if the octanol: water partition coefficients of the compounds were higher than about 3.5. With one compound, otherwise similar to misonidazole, the increased lipophilicity led to about one order of magnitude lower concentration achieving the same degree of radiosensitization. (+info)