Halogenating Enzymes Produced by Marine Algae and Microbes---Structures and Functions

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Many physiologically active, halogenated compounds have been found in marine algae. Haloperoxidases are known to be involved in the biosynthesis of these halometabolites. Our two groups found that some algae and microorganisms produced a large amount of haloperoxidase at the same time and independently. However, concerning algae producing the enzyme, Corallina pilulifera could be available only around Japan, and Ascophyllum nodosum could be only in the North Sea. This circumstance have led to this joint research.Bromoperoxidase was purified from the crude extract of C. pilulifera to complete homogeneity. The content of the enzyme in the alga was as much as 3% the total protein of the crude extract. The enzyme had a molecular mass of ca. 790 kDa and was composed of twelve subunits of identical molecular mass of 64 kDa. The enzyme as isolated contained 4 mol of vanadium per mol of bromoperoxidase (790 kDa). Also the enzyme was found to contain Fe^<3+> and Mg^<2+> abundantly. Ferric ion m … More arkedly shortened the time required for the full activation of the apoenzyme by vanadate. We also studied the application of the enzyme to the production of various halogenated compounds.By the researchers at Amsterdam University the bromoperoxidase from A.nodosum was purified to homogeneity. The enzyme had a molecular mass of 67 kDa, and contained 1 mol of vanadium per mol of bromoperoxidase. It has been revealed that the enzyme was stable even in 40% acetone, methanol, and n-propanol for a month at a room temperature.The chloroperoxidase from the fungi, Curvularia inaequalis, was also purified to homogeneity by the researchers in Amsterdam University. It has shown that histidine residue was involved in the binding site of vanadium for the enzyme.When these enzymes were digested by proteases and compared one another by the electrophoresis, it seemed that they had some similarity. Concerning the enzyme of C. pilulifera, 253 amino acid sequences have been identified. Furthermore, the basic conditions were examined to crystallize the enzyme of C. pilulifera in collaboration with the research group at Imperial College in U.K. Less