caa a22 4500 477118941 CHVBK 20180405111630.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF00227536 doi (NATIONALLICENCE)springer-10.1007/BF00227536 EDTA inhibits lactoperoxidase-catalyzed iodide oxidation by acting, as an electron-donor and interacting near the iodide binding site [Elektronische Daten] [Dipak Bhattacharyya, Uday Bandyopadhyay, Ranajit Banerjee] Ethylenediamine tetraacetate ( EDTA ) inhibits lactoperoxidase (LPO)-catalyzed rate of iodide oxidation in concentration and pH-dependent manner. A plot of log Kiapp values against various pH yields a sigmoidal curve from which an ionisable group of pKa value 6.0 could be ascertained for controlling the inhibition of catalytically active LPO by EDTA. Kinetic studies indicate that EDTA competitively inhibits iodide oxidation by acting as an electron donor. EDTA al so reduces LPO-compound-11 to the native ferric state by one-electron transfer as evidenced by the spectral shift from 428 to 412 nm. Optical difference spectroscopic studies indicate that EDTA binds to LPO with the apparent equilibrium dissociation constant (KD) of 12 ± 2 mM at pH 6.5. A plot of log KD values against various pH produces a sigmoidal curve from which an ionisable group of LPO having pka = 5.47 could be calculated, deprotonation of which favours EDTA binding. EDTA also binds to LPO-CN- complex indicating its binding site away from heme iron centre. The KD of LPO-EDTA complex is significantly increased (62 ± 5 mM) by iodide suggesting that EDTA binds close to the iodide binding site. EDTA also increases the KD value of LPO-hydroquinone complex from 62 ± 5 mM to 200 ± 21 mM indicating that EDTA and aromatic donor binding sites are also close. We suggest that EDTA inhibits iodide oxidation competitively as an electron donor by interacting at or near the iodide binding site and these sites are close to the aromatic donor binding site. Kluwer Academic Publishers, 1996 lactoperoxidase nationallicence EDTA oxidation nationallicence EDTA binding nationallicence iodide oxidation nationallicence EDTA as electron-donor nationallicence Bhattacharyya Dipak Department of Physiology, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, 700032, Calcutta, India aut Bandyopadhyay Uday Department of Physiology, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, 700032, Calcutta, India aut Banerjee Ranajit Department of Physiology, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, 700032, Calcutta, India aut Molecular and Cellular Biochemistry Kluwer Academic Publishers 162/2(1996-09-01), 105-111 0300-8177 162:2<105 1996 162 11010 https://doi.org/10.1007/BF00227536 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00227536 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Bhattacharyya Dipak Department of Physiology, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, 700032, Calcutta, India aut NATIONALLICENCE 700 1- Bandyopadhyay Uday Department of Physiology, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, 700032, Calcutta, India aut NATIONALLICENCE 700 1- Banerjee Ranajit Department of Physiology, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, 700032, Calcutta, India aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Kluwer Academic Publishers 162/2(1996-09-01), 105-111 0300-8177 162:2<105 1996 162 11010 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer