Vanadium chloroperoxidases

Simons BH, P Barnett, EGM Vollenbroek, HL Dekker, AO Muijsers, A Messerschmidt, R Wever (1995) Primary structure and characterization of the vanadium chloroperoxidase from the fungus Curvularia inaequalis. Eur J Biochem 229 566-574. 

Renirie R, W Hemrika, R Wever (2000) Peroxidase and phosphatase activity of active-site mutants of vanadium chloroperoxidase from the fungus Curvularia inaequalis. J Biol Chem 275 11650-11657. 

Figure 17.14 Proposed mechanism for the vanadium chloroperoxidase oxidation of chloride by hydrogen peroxide. (From Ligtenbarg et al., 2003. Copyright 2003, with permission from Elsevier.)...

Enzymes requiring vanadium for catalytic activity. Perhaps the best studied of these are the vanadium-dependent nitrogenases [EC 1.18.6.1]. Other vanadium-dependent enzymes include vanadium haloperoxidase, vanadium chloroperoxidase, and vanadium bromoper-oxidase. In the vanadium chloroperoxidase and bromo-peroxidase reactions, the vanadium(V) is coordinated in a trigonal bipyramidal site to a histidyl residue, three nonprotein oxygens, and, presumably, to a hydroxide. 

Abbreviated proposed mechanism of vanadium chloroperoxidase-catalyzed halogenation 2123, 2124, 2146, 2172, 2173, 2175). 

Simons BH, Barnett P, Vollenbroek EGM, Dekker HL, Muijsers AO, Messerschmidt A, Wever R (1995) Primary Structure and Characterization of the Vanadium Chloroperoxidase from the Fungus Curvularia inaequalis. Eur J Biochem 229 566... 

Barnett P, Hemrika W, Dekker ILL, Muijsers AO, Renirie R, Wever R (1998) Isolation, Characterization, and Primary Structure of the Vanadium Chloroperoxidase from the Fungus Embellisia didymospora. J Biol Chem 273 23381... 

Tanaka N, Hasan Z, Wever R (2003) Kinetic Characterization of Active Site Mutants Ser402Ala and Phe397His of Vanadium Chloroperoxidase from the Fungus Curvularia inaequalis. Inorg Chim Acta 356 288... 

Hasan Z, Renirie R, KerkmanR, Ruijssenaars HJ, Hartog AF, Wever R (2006) Laboratory-Evolved Vanadium Chloroperoxidase Exhibits 100-Fold Higher Halogenating Activity at Alkaline pH. Catalytic Effects from First and Second Coordination Sphere Mutations. J Biol Chem 281 9738... 

Waller MP, Biihl M, Geethalakshmi KR, Wang D, Thiel W (2007) 51V NMR Chemical Shifts Calculated from QM/MM Models of Vanadium Chloroperoxidase. Chem Eur J 13 4723... 

In addition to bromide and iodide, V-BrPO can catalyze the oxidation of chloride [64]. As mentioned previously and discussed more fully later, a distinct enzyme, vanadium chloroperoxidase, has also been discovered. Originally it was thought that V-BrPO could only catalyze the oxidation of bromide and iodide by dihydrogen peroxide. In fact, under the standard mcd bromoperoxidase assay conditions, in which the V-BrPO concentration is ca. nanomolar, very little, if any, chlorination of mcd is observed. However, it seemed very unusual that V-BrPO could be inhibited by fluoride and bromide, but apparently not by chloride [27], In reinvestigating the halide specificity of V-BrPO, it was discovered that when the enzyme concentration is increased 100-fold to 0.1 pM, chlorination is observed at an appreciable rate [64], The specific chloroperoxidase activity is 0.76 U/mg (under conditions of 1 M certified 100% bromide-free KC1, 2 mMH202, 50 pM... 

Vanadium chloroperoxidase (C. inaequalis) is a 67,488 Da protein that comprises 609 amino acid residues, as determined from deoxyribonucleic acid (DNA) sequence analysis [20], As isolated, V-CIPO may contain a variable content of vanadium, depending on the concentration of vanadate in the growth medium however, one vanadium(V) per subunit can be achieved by addition of excess vanadate to the growth medium or to the purified protein [3,71] Like V-BrPO, V-CIPO is stable in the presence of organic substrates, to elevated temperatures, and to the presence of high concentrations of strong oxidants (e.g., HOC1) [59],... 

Recently the amino acid sequence of vanadium chloroperoxidase was determined to have similar stretches with three families of acid phosphatases, which were previously considered unrelated [72], This sequence raises questions about the phosphatase activity of apo-V-ClPO and whether the acid phosphatases can coordinate vanadate and carry out peroxidative halogenation chemistry. In fact, apo-V-C1PO does have phosphatase activity, catalyzing the hydrolysis of/i-nitrophe-nol phosphate (p-NPP). In addition, /i-NPP displaces vanadate from V-CIPO. At this point, the haloperoxidase activity of the acid phosphatases containing coordinated vanadium(V) has not been reported. 

Metalloenzymes contain a bound metal ion as part of their structure. This ion can either partidpate directly in the catalysis, or stabilize the active conformation of the enzyme. In Lewis acid catalysis (typically with zinc, vanadium, and magnesium), the M"+ ion is used instead of H+. Many oxidoreductases use metal centers such as V, Mo, Co, and Fe in much the same way as homogeneous catalysis uses ligand-metal complexes. Figure 5.7 shows a simplified mechanism for the halide oxidation readion catalyzed by vanadium chloroperoxidase. The vanadium atom ads as a Lewis add, activating the bound peroxide [30]. 

Figure 5.7 a Simplified catalytic cycle for vanadium chloroperoxidase, isolated from the fungus Curvularia inaequalis based on b crystal structures ofthe native enzyme and the peroxo intermediate [30,31], Thanks to Dr. Teunie van Herk for the enzyme structure image. 

Hasan, Z., Renirie, R., Kerkman, R., Ruijssenaars, H.J., Hartog, A.F. and Wever, R. (2006) Laboratory-evolved vanadium chloroperoxidase Exhibits 100-fold higher halogenating activity at alkaline pH catalytic effects from first and second coordination sphere mutations. 

Barnett, P, W. Hemrika, H.L. Dekker, A.O. Muijsers, R. Renirie, and R. Wever. 1998. Isolation, characterization, and primary structure of the vanadium chloroperoxidase from the fungus Embellisia didymospor. J. Biol. Chem. 273 23381-23387. 

Figure 1.7 (a) UV-VIS absorption spectra of 100 /solid line shows the apo-enzyme, the upper solid line the holo-enzyme after addition of 100 /xM vanadate. The dotted line is the peroxo-form of the enzyme after addition of 100 /optical absorbance at 316 nm ( ). Absorbance of free vanadate under the same buffer conditions (O). Reprinted with permission from Renirie, R., Hemrika, W., Piersma, S.R. and Wever, R. (2000). Biochemistry, 39, 11 33-1141. Copyright 2000 American Chemical Society. 

Pooransingh-Margolis, N., Renirie, R., Hasan, Z., Wever, R., Vega, A. J. and Polenova, T. (2006). 51V solid-state magic angle spinning NMR spectroscopy of vanadium chloroperoxidase. Journal of the American Chemical Society, 128,5190-5208. 

Renirie, R., Hemrika, W., Piersma, S. R. and Wever, R. (2000a). Cofactor and substrate binding to vanadium chloroperoxidase determined by UV-VIS spectroscopy and evidence for high affinity for pervanadate. Biochemistry, 39,1133-1141. 

Figure 1 Simplified model for the reaction mechanism of the vanadium bromoperoxidases. As we will see later this mechanism may be slightly different for the vanadium chloroperoxidases...

Figure 5 A possible explanation for the difference in reactivity between vanadium chloroperoxidase and bromoperoxidase ...

X-ray Structure of the Vanadium Chloroperoxidase and Details of the Active Site... 

FIGURE 3.6 Active site of vanadium chloroperoxidase from C. inaequalis. 

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