1,721,075 research outputs found
Use of 7-nitro-2,1,3 benzoxadiazole derivatives for anticancer therapy
No full textDerivatives of the heterocyclic compound known as 7-nitro-benzofurazan or 7-nitro-2,1,3-benzoxadiazole,of the general formula (I) are proposed as agents having a strong inhibiting activitytowards members of the glutathione S-transferase (GST) superfamily ..
Glutathione transferases and development of new principles to overcome drug resistance
No full textChemoresistance is a multifactorial phenomenon and many studies clearly show that a coordinated expression of efflux transporter proteins and phase II conjugating enzymes in tumor cells is linked to the development of the multidrug resistance phenotype. In particular, the overexpression of glutathione S-transferases and efflux pumps in tumors may reduce the reactivity of various anticancer drugs. In recent years it has become evident that glutathione S-transferases are also involved in the control of apoptosis through the inhibition of the JNK signaling pathway. As such, the glutathione S-transferase superfamily has become the focus of extensive pharmaceutical research in attempt to generate more efficient anticancer agents. Here we present an overview of the GST inhibitors and the GST-activated pro-drugs utilized to date to overcome drug resistance
Study on the interaction between the skin detoxifying enzyme glutathione S-transferase and the substances listed in the CE/39/2000 rules with the "skin" annotation, finalized to the biological monitoring of exposed subjects
No full textThe interaction among chemicals listed in the Directive CE/39/2000 with skin notation and glutathione S-transferase (GSTP1-1) was studied by following two different experimental approaches. The compounds were incubated with the purified GST isoenzyme GSTP1-1 as well as with the human keratinocytes (PR5) selectively expressing GSTP1-1. Some of the molecules affected the enzymatic activity of both the purified and the intracellular GSTP1-1. In particular, 1,2-dichlorobenzene (DCB), ethylbenzene (ETB), cumene, Sulphotep and 2-eptanone (2-EPT) behaved as inhibitors of the purified GSTP1-1 enzyme, with different inhibition properties according to molecular structure. With the exception of Sulphotep showing a Ki value of 0.2 mM, all compounds reported above were characterized by high Ki values (between 2 and 16 mM) and therefore by low affinity towards GSTP1-1. These results make unlikely the use of a biosensor, based on immobilized GSTP1-1, for the detection of these molecules. On the contrary, Sulphotep can be the object of future investigations. It has to be stressed that the above listed compounds were effective on human keratinocytes, at concentrations two order of magnitude lower than that effective on purified GSTP1-1. In particular, cumene and DCB triggered a clear increase of the intracellular GSTP1-1 activity at concentrations lower than 0.1mM. These interesting results let to hypothesize the use of GSTP1-1 present in the keratinocytes as a marker for biological monitoring of workers exposed to these compounds as well as to evaluate the skin permeability of toxic compounds, not yet identified with a skin notation
Inhibition of human placenta glutathione transferase P1-1 by the antibiotic calvatic acid and its diazocyanide analogue - Evidence for multiple catalytic intermediates
No full textThe inhibition mechanism of the dimeric human placenta glutathione transferase (GST) P1-1 by calvatic acid and the reaction intermediates, i.e. the diazocyanide analogue of calvatic acid, has been investigated at pH 7.0 and 30.0 degrees C. Experiments performed at different molar ratios of inhibitor/GST P1-1 indicate that 1 mol calvatic acid inactivates 1 mol GST P1-1, containing two catalytically equivalent active sites. However, 2 mol of the diazocyanide analogue of calvatic acid inactivate 1 mol GST P1-1. Two disulfide bridges/dimer, probably between Cys47 and Cys101, have been formed during the reaction of GST P1-1 with calvatic acid and its diazocyanide analogue. The apparent second-order rate constants for GST P1-1 inactivation by calvatic acid and its diazocyanide analogue are 2.4 +/- 0.3 M-1 s(-1) and (8.5+/-0.7)x10(3) M-1 s(-1), respectively. The reaction of calvatic acid with free L-cysteine can be described by a simple process with an apparent second-order rate constant of (5.0 +/- 0.4)x10(1) M-1 s(-1). In contrast, a transient species occurs during the reaction of the diazocyanide analogue of calvatic acid with free L-cysteine. Kinetics may be described by second-order process [the rate constant being (8.0+/-0.5)x10(3) M-1 s(-1)] followed by a first-order decay [the rate constant corresponding to (1.2+/-0.1)x10(1) s(-1)]. Calvatic acid represents an enzyme inhibitor acting much slower than its reaction intermediates (i.e. its diazocyanide analogue)
Inhibition of human placenta glutathione transferase P1-1 by the antibiotic calvatic acid and its diazocyanide analogue--evidence for multiple catalytic intermediates
No full textAre the steady state kinetics of glutathione transferase always dependent on the deprotonation of the bound glutathione? New insights in the kinetic mechanism of GST P 1-1
No full textStructural basis for the binding of the anticancer compound 6-(7-Nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol to human glutathione S-transferases
No full textGlutathione S-transferases (GST) constitute a superfamily of enzymes with diversified functions including detoxification from xenobiotics. In many human cancers, Pi class GST (GSTP1-1) is overexpressed and contributes to multidrug resistance by conjugating chemotherapeutics. In addition, GSTP1-1 displays antiapoptotic activity by interacting with c-Jun NH2-terminal kinase, a key regulator of apoptosis. Therefore, GSTP1-1 is considered a promising target for pharmaceutical treatment. Recently, a potent inhibitor of GSTs, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX), was identified and tested on several tumor cell lines demonstrating high antiproliferative activity. To establish the structural basis of NBDHEX activity, we determined the crystal structure of NBDHEX bound to either GSTP1-1 or GSTM2-2 (mu class). NBDHEX in both cases binds to the H-site but occupies different positions. Furthermore, the compound is covalently attached to the GSH sulfur in the GSTM2-2 crystal, forming a S-complex, although it is bound but not conjugated in the GSTP1-1 crystal. Several differences in the H-sites of the two isozymes determine the higher affinity of NBDHEX for GSTM2-2 with respect to GSTP1-1. One such difference is the presence of Ile104 in GSTP1-1 close to the bound NBDHEX, whereas the corresponding position is occupied by an alanine in GSTM2-2. Mutation of Ile104 into valine is a frequent GSTP1-1 polymorphism and we show here that the Ile104Val and Ile104Ala variants display a 4-fold higher affinity for the compound. Remarkably, the GSTP1-1/ Ile104Ala structure in complex with NBDHEX shows a considerable shift of the compound inside the H-site. These data might be useful for the development of new anticancer compounds
Structural flexibility modulates the activity of human glutathione transferase P1-1 - Influence of a poor co-substrate on dynamics and kinetics of human glutathione transferase
No full textInvestigation of the active site of human placenta glutathione transferase pi by means of a spin-labelled glutathione analogue
No full textA spin-labelled analogue of glutathione (sl-glutathione) has been used in order to characterize the active site of human placenta glutathione transferasc pi. The sl-glutathione shows a competitive inhibition towards glutathione (K(i) = 14-mu-M). Binding of sl-glutathione to the enzyme, followed by electron paramagnetic resonance spectroscopy, gives a K(d) of 3-mu-M and two identical binding sites for dimeric unit. Inhibition of the enzyme, by modification of the Cys-47 residue, completely prevents the binding of sl-glutathione. The same results are obtained by monitoring the binding of glutathione by means of fluorescence spectroscopy. It is concluded that integrity of the thiolate of Cvs-47 is necessary to maintain an active conformation of the enzyme able to efficiently bind glutathione into the active site
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