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Reactivity of the horseradish peroxidase compounds I and II toward organometallic substrates. A stopped‐flow kinetic study of oxidation of ferrocenes
Author(s) -
Goral Vasily N.,
Ryabov Alexander D.
Publication year - 1998
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216549800202432
Subject(s) - chemistry , horseradish peroxidase , reactivity (psychology) , reaction rate constant , substrate (aquarium) , ionic strength , steady state (chemistry) , kinetics , medicinal chemistry , electron transfer , catalysis , ionic bonding , stereochemistry , nuclear chemistry , organic chemistry , enzyme , ion , aqueous solution , medicine , physics , alternative medicine , oceanography , pathology , quantum mechanics , geology
Reactivity of horseradish peroxidase compounds I and II (HRP‐I and HRP‐II) toward organometallicic substrates, viz water‐soluble ferrocenes RFc (R = COOH and CH2NMe2), has been studied at 25 °C, pH 6.0 and ionic strength 0.1 M. The second‐order rate constants k2 for the reaction of HRP‐I with FcCOOH and FcCH2NMe2 equal (1.00±0.04)×106 and (0.27±0.01)×106 M‐1 s‐1, respectively. The values of k3 for the reaction of HRP‐II with FcCOOH and FcCH2NMe2 equal (1.1±0.1)×l04 and (0.25±0.01)×104 M‐1 s‐1, respectively. The steady‐state kinetic study of the HRP‐catalyzed oxidation of the ferroeenes by H202 under the same conditions gave the second‐order rate constants of (0.94±0.03)×104 and (0.24±0.06)×104 M‐1 s‐1 for FcCOOH and FcCH2NMe2, respectively, which are in a good agreement with k3. The results reported here confirm the proposal that the rate‐limiting step of the steady‐state oxidation of ferrocenes is the electron transfer from the substrate to HRP‐II.