Inhibition of aldehyde reductase I by some isoquinoline alkaloids

1987 ◽  
Vol 52 (9) ◽  
pp. 2338-2346 ◽  
Author(s):  
Hana Paulová ◽  
Jan Kovář ◽  
Jiří Plocek ◽  
Jiří Slavík
Keyword(s):  
Alcohol Dehydrogenase ◽  
Binding Site ◽  
Inhibitory Action ◽  
Positive Charge ◽  
Aldehyde Reductase ◽  
Isoquinoline Alkaloids ◽  
Active Centre ◽  
Hydrophobic Nature ◽  
Kinetics Of

Aldehyde reductase I has been found to be inhibited by certain isoquinoline alkaloids (protoberberines, protopines, benzylisoquinolines, benzyltetrahydroisoquinolines, phthalideisoquinolines, pavinanes) and narceine imide. The sensitivity of this enzyme to the compounds tested was compared with that of alcohol dehydrogenase and/or aldehyde reductase II to them; alcohol dehydrogenase proved more selective in binding the alkaloids. The kinetics of the inhibitory action of berberine and other results suggest that the binding site of aldehyde reductase I for alkaloids is relatively large, has a hydrophobic nature, and probably contains a group with a positive charge. This binding site is probably not identical with the active centre of the nezyme.

Studies on the interaction of glutamate dehydrogenase with aporheine

1984 ◽  
Vol 49 (9) ◽  
pp. 2001-2011
Author(s):  
Jan Kovář ◽  
Luděk Matyska
Keyword(s):  
Binding Site ◽  
Glutamate Dehydrogenase ◽  
Inhibitory Action ◽  
Positive Charge ◽  
Alkaline Media ◽  
Acidic Ph ◽  
High Affinity ◽  
Good Substrate ◽  
Kinetics Of

The effect was examined of two inhibitors, aporheine and thyroxine, on the kinetics of action of glutamate dehydrogenase in the presence of the coenzyme, NADH, in an inhibiting excess. from the results obtained it appears probable that these two competing ligands do not bind to the regulatory binding site of the enzyme. If the good substrate, glutamate, is replaced by a poor one, such as alanine, aporheine can behave under certain conditions as an activator; this phenomenon is most likely due to fact, like in other cases, that the association of alanine wit the enzyme-coenzyme complex is the slowest step of the reaction. The inhibitory action of aporheine in alkaline media is more complicated than its action at neutral and acidic pH. The sigmoid dependence of inhibition on aporheine concentration is best interpreted as a result of the induction of the second binding site of the enzyme subunit for aporheine after the binding of the first molecule of this ligand. The results obtained indicate the presence of a positive charge localized in the neighborhood of the binding site for the first aporheine molecule and also the important role played by some group of the enzyme with a pK-value about 8 during the induction of the second binding site with a relative high affinity for this ligand.

Iodoacetate inactivation of rape alcohol dehydrogenase

1980 ◽  
Vol 45 (5) ◽  
pp. 1601-1607 ◽  
Author(s):  
Marie Stiborová ◽  
Sylva Leblová
Keyword(s):  
Alcohol Dehydrogenase ◽  
Protein Molecule ◽  
Sulfhydryl Groups ◽  
Inactivation Rate ◽  
First Order ◽  
Ph Dependent ◽  
Kinetics Of

Iodoacetate inactivates rape alcohol dehydrogenase (ADH, EC 1.1.1.1). The inactivation rate follows the kinetics of the first order, is pH-dependent, and decreases below pH 7.5. Besides irreversible alkylation of the sulfhydryl groups of the enzyme iodoacetate also forms a reversible complex with rape ADH. The coenzyme (NAD) and its analogs (ATP, ADP, AMP) competitively protect the enzyme against alkylation; o-phenanthroline also protects the enzyme against alkylation yet noncompetitively with respect to iodoacetate. Imidazole and o-phenanthroline compete with one another for binding to the protein molecule of rape ADH. Whereas o-phenanthroline decreases the inactivation rate imidazole increases the rate of iodoacetate inactivation.

scholarly journals Positive charge of “sticky” peptides and proteins impedes release from negatively charged PLGA matrices

2015 ◽  
Vol 3 (23) ◽  
pp. 4723-4734 ◽  
Author(s):  
Stephen C. Balmert ◽  
Andrew C. Zmolek ◽  
Andrew J. Glowacki ◽  
Timothy D. Knab ◽  
Sam N. Rothstein ◽  
...  
Keyword(s):  
Positive Charge ◽  
Release Kinetics ◽  
P Release ◽  
Kinetics Of

Release kinetics of biomolecules (agents) encapsulated in negatively charged PLGA matrices are slowed by positive charge on the agents.

scholarly journals Positive co-operative binding at two weak lysine-binding sites governs the Glu-plasminogen conformational change

1992 ◽  
Vol 285 (2) ◽  
pp. 419-425 ◽  
Author(s):  
U Christensen ◽  
L Mølgaard
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Conformational Change ◽  
Conformational Changes ◽  
Binding Sites ◽  
High Specificity ◽  
Stopped Flow ◽  
Protein Fluorescence ◽  
Lysine Residues ◽  
Kinetics Of

The kinetics of a series of Glu-plasminogen ligand-binding processes were investigated at pH 7.8 and 25 degrees C (in 0.1 M-NaCl). The ligands include compounds analogous to C-terminal lysine residues and to normal lysine residues. Changes of the Glu-plasminogen protein fluorescence were measured in a stopped-flow instrument as a function of time after rapid mixing of Glu-plasminogen and ligand at various concentrations. Large positive fluorescence changes (approximately 10%) accompany the ligand-induced conformational changes of Glu-plasminogen resulting from binding at weak lysine-binding sites. Detailed studies of the concentration-dependencies of the equilibrium signals and the rate constants of the process induced by various ligands showed the conformational change to involve two sites in a concerted positive co-operative process with three steps: (i) binding of a ligand at a very weak lysine-binding site that preferentially, but not exclusively, binds C-terminal-type lysine ligands, (ii) the rate-determining actual-conformational-change step and (iii) binding of one more lysine ligand at a second weak lysine-binding site that then binds the ligand more tightly. Further, totally independent initial small negative fluorescence changes (approximately 2-4%) corresponding to binding at the strong lysine-binding site of kringle 1 [Sottrup-Jensen, Claeys, Zajdel, Petersen & Magnusson (1978) Prog. Chem. Fibrinolysis Thrombolysis 3, 191-209] were observed for the C-terminal-type ligands. The finding that the conformational change in Glu-plasminogen involves two weak lysine-binding sites indicates that the effect cannot be assigned to any single kringle and that the problem of whether kringle 4 or kringle 5 is responsible for the process resolves itself. Probably kringle 4 and 5 are both participating. The involvement of two lysine binding-sites further makes the high specificity of Glu-plasminogen effectors more conceivable.

scholarly journals Thermodynamics and Molecular Kinetics of Liver Alcohol Dehydrogenase.

1963 ◽  
Vol 17 supl. ◽  
pp. 27-33 ◽  
Author(s):  
Keith Dalziel ◽  
Gad Yagil ◽  
Warren F. Diven ◽  
Mark Takahashi
Keyword(s):  
Alcohol Dehydrogenase ◽  
Liver Alcohol Dehydrogenase ◽  
Kinetics Of

A Study of the "Lipoxidase" in the Flesh of British Columbia Herring

1952 ◽  
Vol 9 (8) ◽  
pp. 393-416 ◽  
Author(s):  
M. M. R. Khan
Keyword(s):  
British Columbia ◽  
Unsaturated Fatty Acids ◽  
Dark Muscle ◽  
Active Centre ◽  
Nitrogenous Compounds ◽  
Sulphydryl Group ◽  
Optimal Activity ◽  
Highly Active ◽  
Enzyme Substrate ◽  
Kinetics Of

From the dark muscle of British Columbia herring a highly active enzyme capable of peroxidizing non-conjugated unsaturated fatty acids was isolated. This "lipoxidase", which was shown to be a nitrogenous complex possessing no heavy metals or sulphydryl group as the active centre, is heat-labile and can act only in presence of activators such as certain iron-containing organic nitrogenous compounds. Two such compounds, namely haemoglobin and cytochrome "c" were isolated. The enzyme exhibits optimal activity at 15 °C. and pH 6.9. There is also an optimal concentration of enzyme, substrate, and of the activators for maximal enzyme activity. The presence of the activators appears to change the kinetics, of the reactions. The inhibition of the enzymic reaction brought about by cyanide and azide is possibly due to the inactivation of the iron-containing activators rather than of the enzyme itself.

scholarly journals Amino acids important in enzyme activity and dimer stability for Drosophila alcohol dehydrogenase

1995 ◽  
Vol 308 (2) ◽  
pp. 419-423 ◽  
Author(s):  
S W Chenevert ◽  
N G Fossett ◽  
S H Chang ◽  
I Tsigelny ◽  
M E Baker ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Alcohol Dehydrogenase ◽  
Binding Site ◽  
Aspartic Acid ◽  
Three Dimensional ◽  
Side Chain ◽  
Wild Type ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Substrate Binding Site

We have determined the nucleotide sequences of eight ethyl methanesulphonate-induced mutants in Drosophila alcohol dehydrogenase (ADH), of which six were previously characterized by Hollocher and Place [(1988) Genetics 116, 253-263 and 265-274]. Four of these ADH mutants contain a single amino acid change: glycine-17 to arginine, glycine-93 to glutamic acid, alanine-159 to threonine, and glycine-184 to aspartic acid. Although these mutants are inactive, three mutants (Gly17Arg, Gly93Glu and Gly184Asp) form stable homodimers, as well as heterodimers with wild-type ADH, in which the wild-type ADH subunit retains full enzyme activity [Hollocher and Place (1988) Genetics 116, 265-274]. Interestingly, the Ala159Thr mutant does not form either stable homodimers or heterodimers with wild-type ADH, suggesting that alanine-159 is important in stabilizing ADH dimers. The mutations were analysed in terms of a three-dimensional model of ADH using bacterial 20 beta-hydroxysteroid dehydrogenase and rat dihydropteridine reductase as templates. The model indicates that mutations in glycine-17 and glycine-93 affect the binding of NAD+. It also shows that alanine-159 is part of a hydrophobic anchor on the dimer interface of ADH. Replacement of alanine-159 with threonine, which has a larger side chain and can hydrogen bond with water, is likely to reduce the strength of the hydrophobic interaction. The three-dimensional model shows that glycine-184 is close to the substrate binding site. Replacement of glycine-184 with aspartic acid is likely to alter the position of threonine-186, which we propose hydrogen bonds to the carboxamide moiety of NAD+. Also, the negative charge on the aspartic acid side chain may interact with the substrate and/or residues in the substrate binding site. These mutations provide information about ADH catalysis and the stability of dimers, which may also be useful in understanding homologous dehydrogenases, which include the human 17 beta-hydroxysteroid, 11 beta-hydroxysteroid and 15-hydroxyprostaglandin dehydrogenases.

scholarly journals The nature of the binding site for aromatic compounds in glycogen phosphorylase b

1975 ◽  
Vol 147 (2) ◽  
pp. 369-371 ◽  
Author(s):  
G Soman ◽  
G Philip
Keyword(s):  
Chemical Modification ◽  
Binding Site ◽  
Aromatic Compounds ◽  
Glycogen Phosphorylase ◽  
Relative Effectiveness ◽  
Rabbit Muscle ◽  
Substituent Constant ◽  
Chemically Modified ◽  
Glycogen Phosphorylase B ◽  
Hydrophobic Nature

The inhibition of rabbit muscle glycogen phosphorylase b (1,4-alpha-D-glucan--orthophosphate alpha-glucosyltransferase, EC 2.4.1.1) by aromatic compounds was examined with 15 compounds. The relative effectiveness of the inhibitors correlated well with increasing substituent constant, pi, indicating the hydrophobic nature of the binding site. The inhibition was not affected by the ionic-strength variation of the assay mixtures. The results predict that the course of chemical modification of this enzyme and the properties of the derivatives depend on the nature of the reagent and on the incorporated groups. Many of the dissimilar and sometimes contradictory results reported for chemical-modification studies and for chemically modified phosphorylase b are explained by the findings presented in the paper.

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