Protonation and hydrogen-bonding state of the distal histidine in the CO complex of horseradish peroxidase as studied by ultraviolet resonance Raman spectroscopy.
نویسندگان
چکیده
Ultraviolet resonance Raman (UVRR) spectroscopy has been used to characterize the structure and hydrogen bonding state of the distal histidine (His42) in horseradish peroxidase (HRP) complexed with carbon monoxide (HRP-CO). The HRP-CO - HRP UVRR difference spectrum in D(2)O solution at pD 7.0 shows two positive peaks at 1408 and 1388 cm(-)(1), which are ascribable to medium-to-weak and strong hydrogen bonding states, respectively, of the protonated imidazolium side chain of His42 in HRP-CO. Both His42 peaks decrease in intensity with increase of pD with a midpoint of transition at pD 8.8, indicating that the pK(a) of His42 in HRP-CO is 8.8. The CO ligand exhibits two C-O stretching Raman peaks at 1932 and 1902 cm(-)(1), the latter of which diminishes at alkaline pD and is assignable to a strong hydrogen-bonded state. It is most probable that the imidazolium side chain of His42 forms a strong hydrogen bond with CO, giving a His42 peak at 1388 cm(-)(1) and a CO peak at 1902 cm(-)(1), in one conformer. The other hydrogen bonding state of His42, giving the 1408 cm(-)(1) peak, is ascribed to another conformer forming a medium-to-weak hydrogen bond with a water molecule in the distal cavity. The present finding that His42 can act as a strong proton donor to CO and decrease the CO bond order is consistent with the role of His42 as a general acid to cleave the O-O bond of hydrogen peroxide, a specific oxidizing agent, in the catalytic cycle of HRP.
منابع مشابه
ELUCIDATION OF pK VALUES FOR ACTIVE SITE OF HORSERADISH PEROXIDASE AND BINDING STUDY OF INTERACTION WITH N-PHENYL BENZHYDROXAMIC ACID USING A SPECIAL DIFFERENCE SPECTROPHOTOMETRIC TECHNIQUE
The binding behavior of a competitive inhibitor, N-phenylbenzhydroxamic acid (BHA) against horseradish peroxidase (HRP) was studied in order to understand and predict the interaction mechanism of hydrogen donors with the enzyme. The dissociation constants of the complexes of HRP-BHA, HRP-donor and HRP-BHA-azide were estimated at specified conditions by difference spectroscopy. The binding s...
متن کاملThe structures of the horseradish peroxidase C-ferulic acid complex and the ternary complex with cyanide suggest how peroxidases oxidize small phenolic substrates.
We have solved the x-ray structures of the binary horseradish peroxidase C-ferulic acid complex and the ternary horseradish peroxidase C-cyanide-ferulic acid complex to 2.0 and 1.45 A, respectively. Ferulic acid is a naturally occurring phenolic compound found in the plant cell wall and is an in vivo substrate for plant peroxidases. The x-ray structures demonstrate the flexibility and dynamic c...
متن کاملSolvent effects on protonation and complexation of histidine with molybdenum (VI) at different aqueous solutions of methanol
The formation constants of the species formed in the systems H+ + Mo(VI) + histidine and H+ +histidine have been determined at different aqueous solutions of methanol (0 - 45 % v/v) at 25 °C andconstant ionic strength (0.1 mol dm-3 sodium perchlorate), using a combination of spectrophotometricand potentiometric techniques. The composition of the complex species was determined by thecontinuous v...
متن کاملThe Unusual Reactivities of Amphitrite ornata Dehaloperoxidase and Notomastus lobatus Chloroperoxidase Do Not Arise from a Histidine Imidazolate Proximal Heme Iron Ligand
Notomastus lobatus chloroperoxidase (NCPO) and Amphitrite ornata dehaloperoxidase (DHP) catalyze the halogenation of phenols and dehalogenation of halophenols, respectively. Both enzymes require peroxide for activity and have recently been shown to contain histidine (His) as their proximal heme iron ligand. DHP is the only heme enzyme known to catalyze peroxide-dependent defluorination reaction...
متن کاملResonance Raman spectroscopy of the catalytic intermediates and derivatives of chloroperoxidase from Caldariomyces fumago.
Near-ultraviolet resonance Raman spectra of chloroperoxidase derivatives and high valent intermediates show frequencies that can be systematically assigned. In accord with previous observations of low v4 frequencies for the ferric enzyme, and quite low v4 frequencies for the ferrous enzyme, low v4 frequencies are observed for ferryl compound II and several ferric derivatives. Resonance Raman sp...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Biochemistry
دوره 45 32 شماره
صفحات -
تاریخ انتشار 2006