scholarly journals Arginine-linked neomycin B dimers: synthesis, rRNA binding, and resistance enzyme activity

MedChemComm ◽  
2016 ◽  
Vol 7 (1) ◽  
pp. 164-169 ◽  
Author(s):  
Yi Jin ◽  
Derrick Watkins ◽  
Natalya N. Degtyareva ◽  
Keith D. Green ◽  
Meredith N. Spano ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Bacterial Rna ◽  
Neomycin B ◽  
A Site

New dimeric aminoglycosides conjugated to arginine were synthesized and found to efficiently bind to human and bacterial RNA A-site and to evade the activity of resistance enzymes.

FURTHER STUDIES ON ENZYMIC INACTIVATION OF LUTEINIZING HORMONE – RELEASING HORMONE (LH-RH) BY PEPTIDASES IN THE RAT HYPOTHALAMUS

1975 ◽  
Vol 79 (1) ◽  
pp. 7-15 ◽  
Author(s):  
E. C. Griffiths ◽  
K. C. Hooper ◽  
C. R. N. Hopkinson
Keyword(s):  
Enzyme Activity ◽  
Luteinizing Hormone ◽  
Assay System ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Rat Hypothalamus ◽  
Lh Rh ◽  
A Site

ABSTRACT Luteinizing hormone-releasing hormone (LH-RH) is known to be inactivated by peptidases in the rat hypothalamus with consequent loss of LH-releasing ability. To make a further study of the peptidases' action on the decapeptide, synthetic LH-RH and its [1–9NH2] analogue were incubated with the supernatant hypothalamic fraction containing the enzyme activity. Using an assay system measuring gonadotrophin release in ovariectomized/steroid-primed rats, both LH-RH and the [1–9NH2] analogue were found to be inactivated to different extents after incubation with the fraction, the analogue completely losing both LH- and FSH-releasing activity, and the releasing hormone almost completely losing its LH- and totally losing its FSH-releasing activity. The findings extend the initial studies by showing that the peptidases can remove both the decapeptide's intrinsic LH- and FSH-releasing activity and that these enzymes act on LH-RH at a site other than the C-terminal glycinamide, since they are able to inactivate the [1–9NH2] analogue lacking this residue.

scholarly journals Influence of Linker Length and Composition on Enzymatic Activity and Ribosomal Binding of Neomycin Dimers

2015 ◽  
Vol 59 (7) ◽  
pp. 3899-3905 ◽  
Author(s):  
Derrick Watkins ◽  
Sunil Kumar ◽  
Keith D. Green ◽  
Dev P. Arya ◽  
Sylvie Garneau-Tsodikova
Keyword(s):  
Enzymatic Activity ◽  
Aminoglycoside Antibiotics ◽  
Substantial Decrease ◽  
Selective Binding ◽  
Linker Length ◽  
Neomycin B ◽  
A Site ◽  
Site Binding

ABSTRACTThe human and bacterial A site rRNA binding as well as the aminoglycoside-modifying enzyme (AME) activity against a series of neomycin B (NEO) dimers is presented. The data indicate that by simple modifications of linker length and composition, substantial differences in rRNA selectivity and AME activity can be obtained. We tested five different AMEs with dimeric NEO dimers that were tethered via triazole, urea, and thiourea linkages. We show that triazole-linked dimers were the worst substrates for most AMEs, with those containing the longer linkers showing the largest decrease in activity. Thiourea-linked dimers that showed a decrease in activity by AMEs also showed increased bacterial A site binding, with one compound (compound 14) even showing substantially reduced human A site binding. The urea-linked dimers showed a substantial decrease in activity by AMEs when a conformationally restrictive phenyl linker was introduced. The information learned herein advances our understanding of the importance of the linker length and composition for the generation of dimeric aminoglycoside antibiotics capable of avoiding the action of AMEs and selective binding to the bacterial rRNA over binding to the human rRNA.

Relationships between denitrification rate and determinant soil properties under barley

1993 ◽  
Vol 73 (4) ◽  
pp. 567-578 ◽  
Author(s):  
D. W. Bergstrom ◽  
E. G. Beauchamp
Keyword(s):  
Enzyme Activity ◽  
Moisture Content ◽  
Soil Properties ◽  
Respiration Rate ◽  
Denitrification Rate ◽  
Bulk Soil ◽  
Small Scale ◽  
Mean Values ◽  
Acetylene Blockage ◽  
A Site

To better understand environmental regulation of denitrification, we examined relationships between denitrification rate and six determinant soil properties: moisture content, air-filled porosity, NO3− content, respiration rate, mineralizable-C concentration and denitrifying enzyme activity (DEA). Soil cores were collected on 27 sampling dates over a growing season at a site seeded to barley (Hordeum vulgare). Denitrification rate was measured using a static core technique and acetylene blockage. Moisture content and air-filled porosity and, to a lesser extent, mineralizable-C concentration and respiration rate were more strongly related to denitrification rate than was DEA. Denitrification rate was unrelated to NO3− content. On most sampling dates, mean denitrification rate increased substantially only below an air-filled porosity of 0.3. Moreover, the distribution of individual measurements of denitrification rate was less skewed at lower air-filled porosities. Approximately 60% of variation in mean values of denitrification rate for each sampling date could be accounted for by measurements of bulk soil properties, of which moisture content and air-filled porosity were most important. Measurements of bulk soil properties did not account for nil values of denitrification rate at low air-filled porosities or for small-scale spatial variability. Such measurements were better indicators of temporal variation — that is, when denitrification occurred — than of actual rates. Key words: Denitrification, air-filled porosity, denitrifying enzyme activity

scholarly journals Contribution of Distinct Structural Elements to Activation of Calpain by Ca2+Ions

2004 ◽  
Vol 279 (19) ◽  
pp. 20118-20126 ◽  
Author(s):  
Anita Alexa ◽  
Zoltán Bozóky ◽  
Attila Farkas ◽  
Peter Tompa ◽  
Peter Friedrich
Keyword(s):  
Enzyme Activity ◽  
Conformational Changes ◽  
Site Directed Mutagenesis ◽  
Schematic Model ◽  
Structural Elements ◽  
Long Distance ◽  
Relay System ◽  
Domain Iii ◽  
A Site ◽  
Mutagenesis Study

The effect of Ca2+in calpain activation is mediated via several binding sites in the enzyme molecule. To test the contribution of structural elements suspected to be part of this Ca2+relay system, we made a site-directed mutagenesis study on calpains, measuring consequential changes in Ca2+binding and Ca2+sensitivity of enzyme activity. Evidence is provided for earlier suggestions that an acidic loop in domain III and the transducer region connecting domains III and IV are part of the Ca2+relay system. Wild-typeDrosophilaCalpain B domain III binds two to three Ca2+ions with aKdof 3400 μm. Phospholipids lower this value to 220 μm. Ca2+binding decreases in parallel with the number of mutated loop residues. Deletion of the entire loop abolishes binding of the ion. The Ca2+dependence of enzyme activity of various acidic-loop mutants of Calpain B and rat m-calpain suggests the importance of the loop in regulating activity. Most conspicuously, the replacement of two adjacent acidic residues in the N-terminal half of the loop evokes a dramatic decrease in the Ca2+need of both enzymes, lowering half-maximal Ca2+concentration from 8.6 to 1.3 mmfor Calpain B and from 250 to 7 μmfor m-calpain. Transducer-region mutations in m-calpain also facilitate Ca2+activation with the most profound effect seen upon shortening the region by deletion mutagenesis. All of these data along with structural considerations suggest that the acidic loop and the transducer region form an interconnected, extended structural unit that has the capacity to integrate and transduce Ca2+-evoked conformational changes over a long distance. A schematic model of this “extended transducer” mechanism is presented.

scholarly journals An anti-peptide antibody targeted to a specific region of rat cytochrome P-450IA2 inhibits enzyme activity

1990 ◽  
Vol 266 (2) ◽  
pp. 497-504 ◽  
Author(s):  
R J Edwards ◽  
A M Singleton ◽  
B P Murray ◽  
D Sesardic ◽  
K J Rich ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Amino Acid Sequences ◽  
Enzyme Inactivation ◽  
Enzyme Linked Immunosorbent Assay ◽  
Variable Regions ◽  
Aryl Hydrocarbon ◽  
Hepatic Microsomes ◽  
Peptide Antibody ◽  
A Site ◽  
Cytochrome P 450

An anti-peptide antibody has been produced which binds to and specifically inhibits the activity of cytochrome P-450IA2 in rat hepatic microsomes. This was achieved by raising an antibody against a synthetic peptide (Ser-Glu-Asn-Tyr-Lys-Asp-Asn), the sequence of which occurs in cytochrome P-450IA2 at positions 290-296. The selection of this region of cytochrome P-450IA2 was based on several criteria, including prediction of surface and loop areas, identification of variable regions between cytochromes P-450IA2 and P-450IA1, and consideration of a site on cytochrome P-450IA1 where chemical modification has been shown to cause substantial enzyme inactivation. The specificity of antibody binding was determined by enzyme-linked immunosorbent assay and by immunoblotting using hepatic microsomal preparations and purified cytochrome P-450 isoenzymes. This showed that the antibody binds specifically to rat and mouse cytochrome P-450IA2 and to no other cytochrome P-450, as was predicted from the amino acid sequences of the peptide and the cytochromes P-450. The effect of the antibody upon enzyme activity was studied in hepatic microsomes from rats treated with 3-methylcholanthrene. The antibody was shown to inhibit specifically the activity of reactions catalysed by cytochrome P-450IA2 (phenacetin O-de-ethylase and 2-acetylaminofluorene activation), but had no effect on aryl hydrocarbon hydroxylase activity, which is catalysed by cytochrome P-450IA1, or on aflatoxin B1 activation.

The fumarate reductase system as a site of anthelmintic attack in Ascaris suum

1984 ◽  
Vol 4 (10) ◽  
pp. 879-883 ◽  
Author(s):  
Margaret M. Barrowman ◽  
Susan E. Marriner ◽  
James A. Bogan
Keyword(s):  
Enzyme Activity ◽  
Ascaris Suum ◽  
Fumarate Reductase ◽  
A Site

Various benzimidazole compounds have been shown to be highly eIIective as inhibitors (up to 50% reduction of activity) in vitro of the helminth-specilic enzyme, fumarate reductase, of Ascaris suum. Anthelmintically active and inactive benzimidazoles were similarly effective as inhibitors of enzyme activity. Albendazole-induced inhibition of Iumarate reductase was not observed when the enzyme was preincubated with NADH.

Eels Under Standing Wave Conditions

1982 ◽  
Vol 40 ◽  
pp. 492-495
Author(s):  
O.L. Krivanek ◽  
J. TaftØ
Keyword(s):  
Standing Wave ◽  
Wave Conditions ◽  
Set Up ◽  
A Site ◽  
Complex Crystal

It is well known that a standing electron wavefield can be set up in a crystal such that its intensity peaks at the atomic sites or between the sites or in the case of more complex crystal, at one or another type of a site. The effect is usually referred to as channelling but this term is not entirely appropriate; by analogy with the more established particle channelling, electrons would have to be described as channelling either through the channels or through the channel walls, depending on the diffraction conditions.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

Head Size and DNA Content in Bacteriophage T4

1972 ◽  
Vol 30 ◽  
pp. 200-201
Author(s):  
Fred Eiserling ◽  
A. H. Doermann ◽  
Linde Boehner
Keyword(s):  
Electron Microscopy ◽  
Dna Content ◽  
Bacteriophage T4 ◽  
Head Size ◽  
Virus Particles ◽  
Altered Protein ◽  
A Cell ◽  
Bacterial Viruses ◽  
A Site ◽  
Protein Shell

The control of form or shape inheritance can be approached by studying the morphogenesis of bacterial viruses. Shape variants of bacteriophage T4 with altered protein shell (capsid) size and nucleic acid (DNA) content have been found by electron microscopy, and a mutant (E920g in gene 66) controlling head size has been described. This mutant produces short-headed particles which contain 2/3 the normal DNA content and which are non-viable when only one particle infects a cell (Fig. 1).We report here the isolation of a new mutant (191c) which also appears to be in gene 66 but at a site distinct from E920g. The most striking phenotype of the mutant is the production of about 10% of the phage yield as “giant” virus particles, from 3 to 8 times longer than normal phage (Fig. 2).

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