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EPR studies on the interaction of lactoperoxidase with endogenous and exogenous anions.
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KINETICS
251
CO40 EPR STUDIES ON THE INTJ3RACTION OF LACTOPEROXIDASE WITH ENDOGENOUS AND EXOGENOUS ANIONS. R. P. Ferraria, P. Cecchinia, E. Laurenti” and I. Sondergaardb aDipartimento di Chimica Inorg. Fis. Mat., Univ. di Torino, I/: P.Giuria z 10125, Torin 0, Italy ‘Department of Biochemistry nnd NutritionT Technical University of Denmark, Copenaghen, Denmark.
(LPO) is a mammalian hemoprotein found in milk tears and saliva. The enzyme, in the presence of H20.2, catalyses the oxidation of thiocyanate ion to hypotiocyanite as the major product which provides in vivo an antimicrobial activity [l]. Our studies on LPO enzymatic system are addressed to better characterize. by using in particular EPR spectroscopy, the native LPO and its interaction with endogenous and exogenous anions [2] around physiologic.al pH. In this context we have been previously investimtion the interaction of SCN.,.:+I. WlL,,r*a;rie LPC by E.pR t&r,iqiie ir, ;I,2 iemIjjr&ire rzrQTe$40 K_ The spectral pattern (20 K) of the LPO-SCN- solution jmolar ratio l:lOj, has been reported in Figure 1 and shows three well resolved absorption lines (gz=287, gy=223. gx =1.67) index of the presence of a lowspin Fe(IIIj heme complex in a rhombic geometry, as the major species. It is well known from -.I 31m 3750 44Qc 2450 NMR binding studies [3] that Gauss the interaction of SCN- with LPO is a prerequisite for its Figure k EPR spectrum of LPOlSCN- system oxidation to OSCN- and it is facilitated by the presence of protonated distal histidine. Indeed the low-spin EPR spectrum of the LPO-SCN- solution, could confirm this hypothesis together with the two electron transfer mechanism proposed for LPO/SCN-/Hz02 system [3]. Lactoperoxidase
7
L
1 et>!,
1. B.Reiter. V.M.Marshall and M.S.Philips, Rez C’et.Sci., 28, 116 (1980). 2 RP.Fcrrari, E.Laurenti, P.C.ec&ini and ISondergaard, in preparation (1993). 3. S.Modi, S.S.Deodhar, Behere D.V. and Mitt-a S., Biochem, 30, 118 (1991).
KINETICS
251
CO40 EPR STUDIES ON THE INTJ3RACTION OF LACTOPEROXIDASE WITH ENDOGENOUS AND EXOGENOUS ANIONS. R. P. Ferraria, P. Cecchinia, E. Laurenti” and I. Sondergaardb aDipartimento di Chimica Inorg. Fis. Mat., Univ. di Torino, I/: P.Giuria z 10125, Torin 0, Italy ‘Department of Biochemistry nnd NutritionT Technical University of Denmark, Copenaghen, Denmark.
(LPO) is a mammalian hemoprotein found in milk tears and saliva. The enzyme, in the presence of H20.2, catalyses the oxidation of thiocyanate ion to hypotiocyanite as the major product which provides in vivo an antimicrobial activity [l]. Our studies on LPO enzymatic system are addressed to better characterize. by using in particular EPR spectroscopy, the native LPO and its interaction with endogenous and exogenous anions [2] around physiologic.al pH. In this context we have been previously investimtion the interaction of SCN.,.:+I. WlL,,r*a;rie LPC by E.pR t&r,iqiie ir, ;I,2 iemIjjr&ire rzrQTe$40 K_ The spectral pattern (20 K) of the LPO-SCN- solution jmolar ratio l:lOj, has been reported in Figure 1 and shows three well resolved absorption lines (gz=287, gy=223. gx =1.67) index of the presence of a lowspin Fe(IIIj heme complex in a rhombic geometry, as the major species. It is well known from -.I 31m 3750 44Qc 2450 NMR binding studies [3] that Gauss the interaction of SCN- with LPO is a prerequisite for its Figure k EPR spectrum of LPOlSCN- system oxidation to OSCN- and it is facilitated by the presence of protonated distal histidine. Indeed the low-spin EPR spectrum of the LPO-SCN- solution, could confirm this hypothesis together with the two electron transfer mechanism proposed for LPO/SCN-/Hz02 system [3]. Lactoperoxidase
7
L
1 et>!,
1. B.Reiter. V.M.Marshall and M.S.Philips, Rez C’et.Sci., 28, 116 (1980). 2 RP.Fcrrari, E.Laurenti, P.C.ec&ini and ISondergaard, in preparation (1993). 3. S.Modi, S.S.Deodhar, Behere D.V. and Mitt-a S., Biochem, 30, 118 (1991).