TY  - GEN
AU  - Tuna,Gamze
TI  - Inhibition characteristics of hypericin on rat small intestine glutathione-S-transferases. 
SN  - 0009-2797
AV  - QU4.3   
PY  - 2010///
PB  - Elsevier
KW  - Biochemistry
KW  - Near East University Article
KW  - Yakın Doğu Üniversitesi Makale
KW  - Pharmacology
KW  - St John's Wort
KW  - Hypericin
N2  - Glutathione-S-transferases constitute a family of enzymes involving in the detoxification of xenobiotics, signalling cascades and serving as ligandins or/and catalyzing the conjugation of various chemicals and drugs. The widely expressed cytosolic GST-pi is a marker protein in various cancers and its increased concentration is linked to drug resistance. GST-pi is autoregulated by S-glutathionylation and it catalyzes the S-glutathionylation of other proteins in response to oxidative or nitrosative stress. S-glutathionylation of GST-pi results in multimer formation and the breakage of ligand binding interactions with c-Jun NH(2)-terminal kinase (JNK). Another widely expressed GST enzyme, GST-alpha is assumed as a marker in hepatocellular damage, is implicated in cancer, asthma, cardiovascular disease and response to chemotherapy. 

Although, it was shown that hypericin binds and inhibits GST-alpha and GST-pi, the inhibition characteristics have not been investigated in detail. The aim of this study was to investigate the effects of hypericin on major GSTs; GST-alpha and GST-pi purified from rat small intestine. When GSH used as varied substrate the inhibition pattern with hypericin was uncompetitive for GST-alpha (K(i) = 0.16 0.02 mu M) and noncompetitive for GST-pi (K(i) =2.46 0.43 mu M). While using CDNB (1-chloro-2,4-dinitrobenzene) as the varied substrate, the inhibition patterns were noncompetitive for GST-alpha and competitive for GST-pi; K(i) values for GST-alpha and GST-pi were 1.91 +/- 0.21 and 0.55 +/- 0.07 mu M, respectively. Since hypericin accumulated in cancer cells and important in photodynamic therapy (PDT), inhibition of GST-alpha and GST-pi by hypericin might increase the effectivity of the treatment. Considering that GST-pi is responsible for the drug resistance its inhibition might increase the benefit obtained from chemotherapy. (C) 2010 Elsevier Ireland Ltd. All rights reserved

UR  - http://library.neu.edu.tr:2048/login?url=http://dx.doi.org/10.1016/j.cbi.2010.07.007 
ER  -