Purification and characterization of bromoperoxidase from Thai seaweeds Polycarvernosa sp.

Abstract

Bromoperoxidase was purified from Thai red seaweeds Polycarvernosa sp. by alcohol precipitation, alkaline precipitation, DEAE cellulose column chromatography and Sephadex G-100 column chromatography. Two types of bromoperoxidase, peak I and peak II, were obtained; they were different in several properties, including kinetic property. Peak I bromoperoxidase had a molecular weingt of 71,000 daltons whereas peak II enzyme had a molecular weingt of 45,000 daltons as determined by sephadex G-100 column chromatography. The isoelectric point of peak I and pesk II bromoperoxidase were 4.7 and 6.8 respectively. The optimum pH of peak I bromoperoxidase was 5.0 whereas that of peak II enzyme was 5.8 Peak I bromoperoxidase was stable in an acidic pH range from 5 to 9 whereas peak II enzyme was stable in an alkaline pH range from 7 to 12. The optimum temperature of peak I and peak II bromoperoxidase were 50 degree C and 55 degree C respectively. Peak I and peak II enzyme had similar thermal stability; 50% fo the activity was lost after incubation at 55 C for 30 min. The spectrum of peak I bromoperoxidase showed the Soret band at 403 nm, a characteristic of hemeprotein. However, the Soret band was not found in the spectrum of peak II enzyme indication that peak II bromoperoxidase was not a hemeprotein. Both peak I and peak II enzyme catalyzed the bromination of monochlorodimedone (MCD), phenol red and xylene cyanol FF. The km values for MCD, phenol red and xylene cyanol FF of peak I were 6.9 x 10(-6)M, 4.4 x 10(-6)M and 3.1 x 10(-6)M respectively. The Km values fro MCD, phenol red and xylene cyanol FF of peak II were 6.4 x 10(-5)M, 1.5 x 10(-5)M and 2.7 x 10(-5)M respectively. The km values for H(,2)O(,2) of peak II were in the range of 10(-5)M for all three organic substrates and the Km values for KBr of peak II enzyme were in the range of 10(-3)-10(-4)M. Activities of both peak I and kpeak II bromoperoxidase were inhibited by azide and cyanide, however peak I was more susceptible to azide inhibition than peak II enzyme. Effect of some effectors on activities of both peak I and peak II bromoperoxidase were also studied