ScienceAsia 32 Supplement 1 (2006): 031-035 |doi: 10.2306/scienceasia1513-1874.2006.32(s1).031

Isolation and Characterisation of Vanadium Bromoperoxidases from Thai Red Alga Gracilaria tenuistipitata

Jirasak Kongkiattikajorn^a* and Pintip Ruenwongsa^b

 
ABSTRACT: Many species of marine macro-algae contain a variety of halogenated secondary metabolites. A halogenating enzyme, haloperoxidase is considered to participate in their syntheses in the presence of halides and hydrogen peroxide. In this study, two enzymes which were isolated and characterised as bromoperoxidases (BPOI and BPOII), with vanadium-dependent activity, have been purified from the red alga Gracilaria tenuistipitata collected in the Eastern Thailand coast, at Ban Laem Sok beach in Trad province. The relative molecular masses were 70 kDa for BPOI and 48 kDa for BPOII as determined by gel filtration. The following kinetic parameters have been determined from a steady-state analysis of the oxidation of bromide by H₂O₂: BPOI, pH_opt = 5.5, K_m(Br^-) = 2.17 x 10^-4 M, K_m(H₂O₂) = 1.0 x 10^-4 M, K_m(MCD) = 2.94 x 10^-5 M; and BPOII, pH_opt = 7.0 , K_m(Br^-) = 4.72 x 10^-5 M, K_m(H₂O₂) = 2.47 x 10-5 M, K_m(MCD) = 8.52 x 10^-4 M. These bromoperoxidases are thermostable, as also observed for other vanadium bromo- and chloro-peroxidases.

Download PDF

a School of Bioresources and Technology, King Mongkut’ s University of Technology Thonburi, Thailand.
b Department of Biochemistry, Mahidol University, Thailand.

* Corresponding author, E-mail: jirasak.kon@kmutt.ac.th