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Modification of Substrate Inhibition of Synaptosomal Acetylcholinesterase by Cardiotoxins
( Seyed Omid Ranaei Siadat ),( Gholam Hosein Riazi ),( Mehdi Sadeghi ),( Long Sen Chang ),( Shinne Ren Lin ),( Peyman Eghtesadi Araghi ),( Gholam Hossein Hakimelahi ),( Ali Akbar Moosavi Movahedi ) 생화학분자생물학회 2004 BMB Reports Vol.37 No.3
Different types of cardiotoxin (I-V and n) were isolated and purified from the venom of the Taiwan cobra (Naja naja atra). The effects of these cardiotoxins were studied on membrane-bound acetylcholinesterase, which was isolated from a sheep`s brain cortex. The results showed that cardiotoxins I-III, V, and n activated the enzyme by modification of substrate inhibition, but cardiotoxin IV`s reaction was different. The inhibition and activation of acetylcholinesterase were linked to the functions of the hydrophobicity index, presence of a cationic cluster, and the accessible arginine residue. Our results indicate that Cardiotoxins have neither a cationic cluster nor an argininge residue in their surface area of loop I; therefore, in contrast to fasciculin, cardiotoxins are attached by loop II to the peripheral site of the enzyme. As a result, fasciculin seems to stabilize nonfunctional conformation, but cardiotoxins seem to stabilize the functional conformation of the enzyme. Based on our experimental and theoretical findings, similar secondary and tertiary structures of cardiotoxins and fasciculin seem to have an opposite function once they interact with acetylcholinesterase. s
Sheng-Huei Yang,Ching-Ming Chien,Mei-Chin Lu,Yi-Hsiung Lin,Xiu-Wei Hu,Shinne-Ren Lin 생화학분자생물학회 2006 Experimental and molecular medicine Vol.38 No.4
Cardiotoxin III (CTX III), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. CTX III-induced K562 cell apoptosis was confirmed by DNA fragmentation (DNA ladder, sub-G1 for-mation) and phosphatidylserine (PS) externalization with an IC50 value of 1.7 g/ml at 48 h. A mechanistic analysis demonstrated that CTX III-induced apop-totic cell death was accompanied by up-regulation of both Bax and endonuclease G (Endo G), and downregulation of Bcl-XL. CTX III had no effect on the levels of Bcl-2, Bid, XIAP survivin, and AIF proteins. CTX III treatment caused loss of the mitochondrial membrane potential (Ψm), release of mitochon-drial cytochrome c to the cytosol, and activation of both caspase-9 and -3. CTX III-induced apoptosis was significantly blocked by the broad-spectrum cas-pase inhibitor Z-VAD-FMK. However, CTX III did not generate reactive oxygen species (ROS) and talase, did not block CTX III-induced apoptosis in K562 cells. Modulation of Bax, Bcl-XL, and the Endo G proteins, release of mitochondrial cytochome c, and activation of caspase-3 and -9 all are involved in the CTX III-triggered apoptotic process in human leukemia K562 cells.
Modification of Substrate Inhibition of Synaptosomal Acetylcholinesterase by Cardiotoxins
Ranaei-Siadat, Seyed-Omid,Riazi, Gholam-Hosein,Sadeghi, Mehdi,Chang, Long-Sen,Lin, Shinne-Ren,Eghtesadi-Araghi, Peyman,Hakimelahi, Gholam Hossein,Moosavi-Movahedi, Ali Akbar Korean Society for Biochemistry and Molecular Biol 2004 Journal of biochemistry and molecular biology Vol.37 No.3
Different types of cardiotoxin (I-V and n) were isolated and purified from the venom of the Taiwan cobra (Naja naja atra). The effects of these cardiotoxins were studied on membrane-bound acetylcholinesterase, which was isolated from a sheep's brain cortex. The results showed that cardiotoxins I-III, V, and n activated the enzyme by modification of substrate inhibition, but cardiotoxin IV's reaction was different. The inhibition and activation of acetylcholinesterase were linked to the functions of the hydrophobicity index, presence of a cationic cluster, and the accessible arginine residue. Our results indicate that Cardiotoxins have neither a cationic cluster nor an arginine residue in their surface area of loop I; therefore, in contrast to fasciculin, cardiotoxins are attached by loop II to the peripheral site of the enzyme. As a result, fasciculin seems to stabilize nonfunctional conformation, but cardiotoxins seem to stabilize the functional conformation of the enzyme. Based on our experimental and theoretical findings, similar secondary and tertiary structures of cardiotoxins and fasciculin seem to have an opposite function once they interact with acetylcholinesterase.