Vanadate-dependent haloperoxidases

Professor M. R. Maurya is currently heading the Department of Chemistry, IIT Roorkee. He has more than 26 years of teaching and research experience. He had worked in Loyola University of Chicago, USA, Iowa State University, Ames, Iowa, USA, National Chemical Laboratory, Pune, and Pune University Pune, before joining department of Chemistry at IIT Roorkee in 1996 and became full professor in 2008. His current area of research interests include structural and functional models of vanadate-dependent haloperoxidases, coordination polymers and their catalytic study, metal complexes encapsulated in zeolite cages and their catalytic study, polymer-anchored metal complexes and their catalytic study, and medicinal aspects of coordination compounds. So far, he has guided 21 doctoral and 7 Master s theses, co-authored more than 140 research papers in the international refereed journals. 

Applications to specific biological systems containing vanadium will be addressed in some detail in the context of the respective subsections of Chapter 4 on naturally occurring vanadium compounds vanadium in sea squirts (e.g. Figure 4.3), vanadate-dependent haloperoxidases (e.g. Table 4.5) and vanadium nitrogenases (e.g. Table 4.8). The central messages, including key references, are briefly summarised here. 

Organisms containing vanadate-dependent haloperoxidases. The enzymes from the algae A. nodosum and Cor. officinalis and the lichen X parietina are hromoperoxidases, and the fungal enzyme (Cur. inaequalis, shown with sporangia) is a chloroperoxidase. 

In the vanadate-dependent haloperoxidases, an 0x0 group of the vanadate centre is exchanged for peroxide prior to 0x0 transfer, referred to as an activation of peroxide, and 0x0 transfer to a substrate such as halide or R2S is afforded by nucleophilic attack of the substrate to the activated (hydro)peroxide as shown in Figure 4.18. Generally, peroxovanadium complexes can thus be considered to model the active catalytic site in the haloperoxidases. A mechanism for the peroxovanadium complex formation as depicted in Equation (4.14), proposed by Pecoraro and co-workersl on the basis of... 

Complexes which model structural and spectroscopic features of the reduced (VO +) form of vanadate-dependent haloperoxidases. 

VI-IX are structurally characterised, vanadate-inhibited phosphatases. VI, Rat prostat acid phosphatase VII, bovine phosphotyrosyl phosphatase VIII, mammalian protein tyrosine phosphatase PTP-IB (mutant Cys215Ser) IX, E. coli alkaline phosphatase. For comparison, the active centre of vanadate-dependent haloperoxidases (VHPO) (V), is also shown. The structures Xa and Xb have been proposed, based on EPR, for the vanadyl complexes formed with the PTP-IB active site peptide Val-His-Cys-Ser-Ala-Gly. 

---