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1

Reduction of milk allergenicity using new synthesized Cu(II) complex as artificial protease

100%
Divsalar A., Saboury A. A., Mansouri-Torshizi H.
Polish Journal of Food and Nutrition Sciences
|
2011
|
tom 61
|
nr Suppl.1
2

The role of alkyl chain length in the inhibitory effect n-alkyl xanthates on mushroom tyrosinase activities

100%
Saboury A. A., Alijanianzadeh M., Mansoori-Torshizi H.
Acta Biochimica Polonica
|
2007
|
tom 54
|
nr 1
Sodium salts of four n-alkyl xanthate compounds, C2H5OCS2Na (I), C3H7OCS2Na (II), C4H9OCS2Na (III), and C6H13OCS2Na (IV) were synthesized and examined for inhibition of both cresolase and catecholase activities of mushroom tyrosinase (MT) in 10 mM sodium phosphate buffer, pH 6.8, at 293 K using UV spectrophotemetry. 4-[(4-methylbenzo)azo]-1,2-benzendiol (MeBACat) and 4-[(4-methylphenyl)azo]-phenol (MePAPh) were used as synthetic substrates for the enzyme for catecholase and cresolase reactions, respectively. Lineweaver-Burk plots showed different patterns of mixed, competitive or uncompetitive inhibition for the four xanthates. For the cresolase activity, I and II showed uncompetitive inhibition but III and IV showed competitive inhibition pattern. For the catecholase activity, I and II showed mixed inhibition but III and IV showed competitive inhibition. The synthesized compounds can be classified as potent inhibitors of MT due to their Ki values of 13.8, 11, 8 and 5 μM for the cresolase activity, and 1.4, 5, 13 and 25 μM for the catecholase activity for I, II, III and IV, respectively. For the catecholase activity both substrate and inhibitor can be bound to the enzyme with negative cooperativity between the binding sites (α > 1) and this negative cooperativity increases with increasing length of the aliphatic tail of these compounds. The length of the hydrophobic tail of the xanthates has a stronger effect on the Ki values for catecholase inhibition than for cresolase inhibition. Increasing the length of the hydrophobic tail leads to a decrease of the Ki values for cresolase inhibition and an increase of the Ki values for catecholase inhibition.
3

Structural and functional changes of bovine carbonic anhydrase as a consequence of temperature

100%
Sarraf N. S., Saboury A. A., Ranjbar B., Moosavi-Movahedi A. A.
Acta Biochimica Polonica
|
2004
|
tom 51
|
nr 3
The temperature dependence of the activity and structure of the enzyme carbonic anhydrase was studied. The Arrhenius plot shows a jump which is seen usually in proteins with more than one subunit or with one subunit but more than one domain. Since carbonic anhydrase has only one subunit with one domain, the fine conformational changes of the protein motifs could only be detected through circular dichroism polarimetry. It seems that the jump in Arrhenius plot is a result of some slight structural changes in the secondary and tertiary structures of the enzyme.
4

Evaluation of p-phenylene-bis and phenyl dithiocarbamate sodium salts and inhibitors of mushroom tyrosinase

88%
Amin E., Saboury A. A., Mansouri-Torshizi H., Zolghadri S., Bordbar A.-K.
Acta Biochimica Polonica
|
2010
|
tom 57
|
nr 3
 Two structurally related compounds, phenyl dithiocarbamate sodium salt (I) and p-phenylene-bis (dithiocarbamate) sodium salt (II) were prepared by reaction of the parent aniline and p-phenylenediamine with CS2 in the presence of sodium hydroxide. These water soluble compounds were characterized by spectroscopic techniques, IR, 1H NMR and elemental analysis. The inhibitory effects of both compounds on both activities of mushroom tyrosinase (MT) from Agricus bisporus were studied at two temperatures, 27ºC and 37ºC. L-3, 4-dihydroxyphenylalanine (L-DOPA), and l-tyrosine were used as natural substrates for the catecholase and cresolase enzyme reactions, respectively. Kinetic analysis confirmed noncompetitive inhibition mode of I and mixed type of II on both activities of MT; I and II inhibit MT with inhibition constants (KI) of 300 μM and 4 μM, respectively. Analysis of thermodynamic parameters indicated predominant involvement of hydrophobic interactions in binding of I and electrostatic ones in binding of II to MT. It seems that II is a more potent MT inhibitor due to its two charged head groups able to chelate copper ions in the enzyme active site. Intrinsic fluorescence studies as a function of concentrations of both compounds showed unexpectedly quenching of emission intensity without any shift of emission maximum. Extrinsic ANS-fluorescence indicated that only binding of I induces limited changes in the tertiary structure of MT, in agreement with the postulated hydrophobic nature of the binding mechanism.
5

Effects of pH on the activity and structure of choline oxidase from Alcaligenes species

88%
Hekmat A., Saboury A. A., Moosavi-Movahedi A. A., Ghourchian H., Ahmad F.
Acta Biochimica Polonica
|
2008
|
tom 55
|
nr 3
549-557
A reversible effect of pH on the ionization of amino-acid residues at the active center of choline oxidase was observed near the optimum pH (8). Inactivation of choline oxidase took place in the pH ranges 3–6 and 9–11, in which irreversible changes in the structure occur leading to the enzyme inactivation. The first order rate constants of the enzyme’s inactivation at various pH values were estimated for the irreversible changes. The Arrhenius analysis revealed no significant changes in the activation enthalpy, while an increase in the activation entropy reflected an increase in the conformational freedom.
6

Inhibition study of adenosine deaminase by caffeine using spectroscopy and isothermal titration calorimetry

76%
Saboury A. A., Divsalar A., Ataie G., Amanlou M., Moosavi-Movahedi A. A., Hakimelahi G. H.
Acta Biochimica Polonica
|
2003
|
tom 50
|
nr 3
Kinetic and thermodynamic studies were made on the effect of caffeine on the activ­ity of adenosine deaminase in 50 mM sodium phosphate buffer, pH 7.5, using UV spectrophotometry and isothermal titration calorimetry (ITC). An uncompetitive inhi­bition was observed for caffeine. A graphical fitting method was used for determina­tion of binding constant and enthalpy of inhibitor binding by using isothermal titra­tion microcalorimetry data. The dissociation-binding constant is equal to 350 uM by the microcalorimetry method, which agrees well with the value of 342 uM for the inhi­bition constant that was obtained from the spectroscopy method. Positive dependence of caffeine binding on temperature indicates a hydrophobic interaction.
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