scholarly journals Two invertebrate acetylcholinesterases show activation followed by inhibition with substrate concentration

1998 ◽  
Vol 329 (2) ◽  
pp. 329-334 ◽  
Author(s):  
Véronique MARCEL ◽  
Laurent Gagnoux PALACIOS ◽  
Christophe PERTUY ◽  
Patrick MASSON ◽  
Didier FOURNIER
Keyword(s):  
Drosophila Melanogaster ◽  
Caenorhabditis Elegans ◽  
Substrate Concentration ◽  
Substrate Activation ◽  
Excess Substrate ◽  
Catalytic Behaviour ◽  
Increased Activity ◽  
Substrate Concentrations ◽  
Single Enzyme

In vertebrates there are two cholinesterases, with differences in catalytic behaviour with respect to substrate concentration: butyrylcholinesterase displays an increased activity at low substrate concentrations, whereas acetylcholinesterase displays inhibition by excess substrate. In two invertebrates, Drosophila melanogaster and Caenorhabditis elegans, we found cholinesterases that showed both kinetic complexities: substrate activation at low substrate concentrations followed by inhibition at higher concentrations. These triphasic kinetics can be explained by the presence of two enzymes with different kinetic behaviours or more probably by the existence of a single enzyme regulated by the substrate concentration.

scholarly journals Substrate Inhibition in the Hydrolysis of Hippuric Acid Esters by Carboxypeptidase A

1975 ◽  
Vol 53 (2) ◽  
pp. 283-294 ◽  
Author(s):  
Joe Murphy ◽  
John W. Bunting
Keyword(s):  
Substrate Concentration ◽  
Hippuric Acid ◽  
Substrate Inhibition ◽  
Competitive Inhibitor ◽  
Side Chain ◽  
Carboxypeptidase A ◽  
Substrate Activation ◽  
Hydrolysis Of ◽  
Substrate Concentrations ◽  
Acid Esters

The dependence of initial velocity upon substrate concentration has been examined in the carboxypeptidase A catalyzed hydrolysis of the following hippuric acid esters (at pH 7.5, 25°, ionic strength O.5): C6H5CONHCH2CO2CHRCO2H: R=CH3; CH2CH3;(CH2)2CH3; (CH2)3CH3; (CH2)5CH3; CH(CH3)2; CH2CH(CH3)2; C6H5; CH2C6H5. All of these esters display marked substrate inhibition of their enzymic hydrolyses. With the exception of R=CH3, the velocity-substrate concentration profiles for each of these esters can be rationalized by the formation of an E.S2 complex which, independent of the alcohol moiety of the ester, reacts approximately 25 times more slowly than the E.S complex. For most of these esters, the formation of E.S2 approximates ordered binding of the substrate molecules at the catalytic and inhibitory sites. While binding at the catalytic site is markedly dependent on the nature of the R group, binding of a second substrate molecule to E.S is not significantly affected by the nature of the R side chain. For R=C6H5, the D ester is neither a substrate nor a competitive inhibitor of the hydrolysis of the L-ester but can replace the L-ester at the binding site which is responsible for substrate inhibition. The kinetic analysis suggests that this behavior of D and L -enantiomers is also typical of the other esters examined (except possibly R=CH3). For R=CH3 only, substrate activation also seems to occur prior to the onset of substrate inhibition at higher substrate concentrations.

Multiplication of a Klebsiella pneumoniae Strain in Water at Low Concentrations of Substrates

1988 ◽  
Vol 20 (11-12) ◽  
pp. 117-123 ◽  
Author(s):  
D. van der Kooij ◽  
W. A. M. Hijnen
Keyword(s):  
Amino Acids ◽  
Water Treatment ◽  
Klebsiella Pneumoniae ◽  
Substrate Concentration ◽  
Treatment System ◽  
Water Treatment System ◽  
Low Concentrations ◽  
Ks Values ◽  
Substrate Concentrations

A K.pneumoniae strain, isolated from a water treatment system, was tested in growth measurements for its ability to multiply at substrate concentrations of a few micrograms per liter. The organism multiplied on mixtures of carbohydrates and amino acids at a substrate concentration of 1 µg of C of each compound per liter. Tests with individual compounds revealed that especially carbohydrates were utilized at low concentrations. The Ks values obtained for maltose and maltopentaose were 53 µg of C/l and 114 µg of C per liter, respectively. The significance of the growth of K.pneumoniae at low substrate concentrations is discussed.

scholarly journals The determination of binding parameters when the total and free substrate concentrations are not approximately equal

1979 ◽  
Vol 179 (3) ◽  
pp. 697-700 ◽  
Author(s):  
N Gains
Keyword(s):  
Substrate Concentration ◽  
Graphical Method ◽  
Enzyme Concentration ◽  
Binding Parameters ◽  
Free Concentration ◽  
Equilibrium Binding ◽  
Substrate Concentrations

By using a standard graphical method values of Km and V may be found that are independent of the conditions and assumptions that the total substrate concentration approximates to its free concentration and that Km is much larger than the enzyme concentration. The procedure is also applicable to the determination of equilibrium binding parameters of a ligand to a macromolecule.

scholarly journals Drosophila Ana2 is a conserved centriole duplication factor

2010 ◽  
Vol 188 (3) ◽  
pp. 313-323 ◽  
Author(s):  
Naomi R. Stevens ◽  
Jeroen Dobbelaere ◽  
Kathrin Brunk ◽  
Anna Franz ◽  
Jordan W. Raff
Keyword(s):  
Drosophila Melanogaster ◽  
Caenorhabditis Elegans ◽  
De Novo ◽  
Protein Family ◽  
Centriole Duplication

In Caenorhabditis elegans, five proteins are required for centriole duplication: SPD-2, ZYG-1, SAS-5, SAS-6, and SAS-4. Functional orthologues of all but SAS-5 have been found in other species. In Drosophila melanogaster and humans, Sak/Plk4, DSas-6/hSas-6, and DSas-4/CPAP—orthologues of ZYG-1, SAS-6, and SAS-4, respectively—are required for centriole duplication. Strikingly, all three fly proteins can induce the de novo formation of centriole-like structures when overexpressed in unfertilized eggs. Here, we find that of eight candidate duplication factors identified in cultured fly cells, only two, Ana2 and Asterless (Asl), share this ability. Asl is now known to be essential for centriole duplication in flies, but no equivalent protein has been found in worms. We show that Ana2 is the likely functional orthologue of SAS-5 and that it is also related to the vertebrate STIL/SIL protein family that has been linked to microcephaly in humans. We propose that members of the SAS-5/Ana2/STIL family of proteins are key conserved components of the centriole duplication machinery.

New BEL-like LTR-retrotransposons in Fugu rubripes , Caenorhabditis elegans , and Drosophila melanogaster

Gene ◽  
2001 ◽  
Vol 263 (1-2) ◽  
pp. 219-230 ◽  
Author(s):  
Ian G Frame ◽  
John F Cutfield ◽  
Russell T.M Poulter
Keyword(s):  
Drosophila Melanogaster ◽  
Caenorhabditis Elegans ◽  
Fugu Rubripes ◽  
Ltr Retrotransposons

CAENORHABDITIS ELEGANS, GALLERIA MELLONELLA E DROSOPHILA MELANOGASTER COMOMODELOS ALTERNATIVOS PARA PESQUISA IN VIVO DE PLANTAS MEDICINAIS

2021 ◽  
pp. 156-163
Author(s):  
Raquel Borges de Barros Primo ◽  
Jacenir Vieira da Silva ◽  
Larissa P. Mueller ◽  
Flávio H. S. Araújo ◽  
Silvia Aparecida Oesterreich
Keyword(s):  
Drosophila Melanogaster ◽  
Caenorhabditis Elegans ◽  
Galleria Mellonella

Effective Substrate Loading for Saccharification of Corn Cob and Concurrent Production of Lignocellulolytic Enzymes by Fusarium oxysporum and Sporothrix carnis

2020 ◽  
Vol 8 (2) ◽  
pp. 109-115
Author(s):  
Folasade M. Olajuyigbe ◽  
Cornelius O. Fatokun ◽  
Oluwatosin I. Oni
Keyword(s):  
Fusarium Oxysporum ◽  
Substrate Concentration ◽  
Reducing Sugars ◽  
Cost Effective ◽  
Reducing Sugar ◽  
Lignocellulolytic Enzymes ◽  
Corn Cob ◽  
Lignocellulosic Wastes ◽  
Single Process ◽  
Substrate Concentrations

Background: One of the critical challenges of cost-effective bioethanol production from lignocellulosic biomass is the decreasing yield of reducing sugars caused by increasing substrate loading. Hence, it is crucial to determine the best substrate concentration for efficient saccharification of lignocellulosic wastes. Objective: This paper reports the saccharification of corn cob by two lignocellulolytic fungi (Fusarium oxysporum and Sporothrix carnis) and concurrent production of lignocellulolytic enzymes at varying substrate concentrations. Methods: F. oxysporum and S. carnis were cultivated on corn cob based media at 30°C and 160 rpm for 144 h. The lignocellulosic composition of corn cob was determined. Saccharification of varying concentrations of substrate was determined by evaluating the release of reducing sugar while the production of cellulase and xylanase was monitored. Results: Cellulose, hemicellulose and lignin contents of corn cob were 37.8±1.56%, 42.2±1.68% and 12.7±1.23%, respectively. Yields of reducing sugar by F. oxysporum and S. carnis were 5.03 µmol/mL and 6.16 µmol/mL; and 6.26 µmol/mL and 6.58 μmol/mL at 10.0 and 25.0% substrate concentration, respectively. The production of cellulase and xylanase was exponential as corn cob concentration increased from 0.5% to 10.0% yielding 586.93 U/mL and 1559.18 U/mL from F. oxysporum, with 590.7 U/mL and 1573.95 U/mL from S. carnis, respectively. Conclusion: The study shows that the most efficient saccharification of corn cob by F. oxysporum and S. carnis was achieved at 10.0% substrate concentration. This suggests that two separate saccharification processes at this concentration will result in higher yields of enzyme and reducing sugars than a single process involving higher concentration.

Influence of substrate concentration on the activation of transketolase, aspartate aminotransferase, and glutathione reductase by coenzymes.

1984 ◽  
Vol 30 (1) ◽  
pp. 143-144
Author(s):  
J C Hafkenscheid ◽  
C M van Dijk
Keyword(s):  
Catalytic Activity ◽  
Glutathione Reductase ◽  
Aspartate Aminotransferase ◽  
Substrate Concentration ◽  
Activity Concentrations ◽  
Influence Of Substrate ◽  
Underlying Mechanisms ◽  
Substrate Concentrations

Abstract We investigated the mechanism by which the three most commonly measured enzymes in erythrocytes are activated by their respective coenzymes by determining the catalytic activity concentrations of transketolase (EC 2.2.1.1), aspartate aminotransferase (EC 2.6.1.1), and glutathione reductase (EC 1.6.4.2) in relation to various substrate concentrations. We conclude that the underlying mechanisms by which the enzymes are activated are not the same.

scholarly journals Quantitative imaging of sleep behavior in Caenorhabditis elegans and larval Drosophila melanogaster

2019 ◽  
Vol 14 (5) ◽  
pp. 1455-1488 ◽  
Author(s):  
Matthew A. Churgin ◽  
Milan Szuperak ◽  
Kristen C. Davis ◽  
David M. Raizen ◽  
Christopher Fang-Yen ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Caenorhabditis Elegans ◽  
Quantitative Imaging ◽  
Sleep Behavior
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