Epoxidation of alkenes by chloroperoxidase catalysis.

Chloroperoxidase from Caldariomyces fumago catalyzes the peroxidation of alkenes to epoxides. This enzyme is the only haloperoxidase of four tested capable of carrying out the reaction. These results further establish chloroperoxidase as a unique haloperoxidase, and adds this enzyme to the short list of other enzymes (e.g., cytochrome P-450) known to epoxidize alkenes.

DMSO is a substrate for chloroperoxidase.

Dimethyl sulfoxide has been used as a nonaqueous organic solvent in haloperoxidase reactions. However, it has been found that this solvent is not inert under chloroperoxidase reaction conditions, forming the halosulfoxide, the sulfone, and the halosulfone. The biological significance of this finding is briefly discussed.

Peroxide oxidation of primary alcohols to aldehydes by chloroperoxidase catalysis.

Chloroperoxidase catalyzes the peroxidation of primary alcohols, specifically those that are allylic, propargylic, or benzylic. Aldehydes are the products. The reaction displays appreciable activity throughout the entire pH range investigated, namely pH 3.0-7.0. This enzyme is the only haloperoxidase of four tested capable of carrying out the reaction. These results further establish chloroperoxidase as a unique haloperoxidase.

Novel haloperoxidase reaction: synthesis of dihalogenated products.

The enzymatic synthesis of vicinal, dihalogenated products from alkenes and alkynes is described. The enzymatic reaction required an alkene or alkyne, dilute hydrogen peroxide, a haloperoxidase, and molar amounts of halide ions. Vicinal dichloro, dibromo, and diiodo products could be formed. A hydroxyl group on the carbon adjacent to the carbon-carbon double or triple bond lowered the halide ion concentration needed to produce the dihalo product. This reaction offers one explanation for the origin of natural, vicinal, dihalogenated products, such as those found frequently in marine microogranisms.

Production of Epoxides from alpha,beta-Halohydrins by Flavobacterium sp.

The relative activity of Flavobacterium whole cells on the enzymatic synthesis of epoxides from alpha,beta-chlorohydrins, -bromohydrins, and -iodohydrins is described.

Novel haloperoxidase substrates. Alkynes and cyclopropanes.

Two new substrate classes that can be halogenated by haloperoxidase have been discovered. The enzymatic halogenation of alkynes yields alpha-halogenated ketones, and the enzymatic halogenation of cyclopropanes yields alpha, gamma-halohydrins. The general reaction scheme proposed involves the initial formation of hypohalous acid as the key intermediate. This proposed mechanism, based upon observed differences in product selectivities, is opposite of that proposed previously, based upon observed differences in substrate selectivities. The biosynthetic implications of these novel haloperoxidase reactions are also discussed.

Neighboring group migration in enzyme-mediated halohydrin formation.

Enzymatic halogenation of the double bond in allyl halides was influenced by intramolecular participation of the allylic halogen in the substrate molecule. Migration of the allylic halogen to the central carbon atom was observed in the enzymatic chlorination of allyl bromide, but not in the enzymatic bromination of allyl chloride. These results parallel the neighboring group effects observed for non-enzymatic halogenation of allyl halides.

Haloperoxidases: Enzymatic Synthesis of alpha,beta-Halohydrins from Gaseous Alkenes.

The enzymatic synthesis of alpha,beta-halohydrins from gaseous alkenes is described. The enzymatic reaction required an alkene, a halide ion, dilute hydrogen peroxide, and a haloperoxidase enzyme. A wide range of gaseous alkenes were suitable for this reaction, including those containing isolated, conjugated, and cumulative carbon-carbon double bonds. Chlorohydrins, bromohydrins, and iodohydrins could be formed. The combining of this enzymatic synthesis with a previously described enzymatic synthesis of epoxides from alpha,beta-halohydrins provides an alternate pathway, other than the well-known enzymatic direct epoxidation pathway, from alkene to an epoxide.