Characterization of nonheme type bromoperoxidase in Corallina pilulifera.

Bromoperoxidase was purified from the crude extract of Corallina pilulifera to be homogeneous upon polyacrylamide disc gel and sodium dodecyl sulfate-polyacrylamide gel electrophoreses according to the procedures previously reported (Itoh, N., Izumi, Y., and Yamada, H. (1985) Biochem. Biophys. Res. Commun. 131, 428-435). The enzyme had a molecular weight of approximately 790,000 and was composed of 12 subunits of identical molecular weights (Mr 64,000). Hexagonal molecular shapes of the enzyme were observed by electron microscopy. The isoelectric point of the enzyme was 3.0, and the predominance of acidic amino acids was revealed by amino acid analysis of the enzyme. The enzyme was specific for I- and Br- and inactive toward Cl- and F-. The optimum pH of the enzyme was 6.0, and the enzyme was stable in a range from pH 5.0 to 11.0. The enzyme had no hemeor flavin-like compounds as a prosthetic group. Plasma emission spectroscopy revealed that the enzyme contains 2.3 +/- 0.2 atoms of iron and 1.6 +/- 0.1 atoms of magnesium/molecule of protein. Hence, bromoperoxidase of C. pilulifera was distinct from other haloperoxidases and many peroxidases, which are hemoproteins.