Demetrios J. Dalietos

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.

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.

Saturated and Unsaturated Wax Esters Produced by Acinetobacter sp. HO1-N Grown on C16-C20 n-Alkanes

The wax ester compositions produced by the action of Acinetobacter sp. HO1-N on n-alkanes (C16 through C20) were analyzed using capillary gas chromatography/mass spectrometry (GC/MS). The wax esters contained, surprisingly, a large percentage of mono-and diunsaturated components. The acyl and alkoxy segments are reported for each wax ester component. Also, the positions of the carbon-carbon double bonds in the wax esters produced from the C16 and C20 n-alkanes are reported. These microbial-produced wax ester mixtures bear a close chemical similarity to those of sperm whale and jojoba oils.

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.

Halonium ion-induced biosynthesis of chlorinated marine metabolites

Abstract Bromoperoxidases do not directly oxidize the chloride ion; nevertheless, in the presence of bromide ions, chloride ions and hydrogen peroxide, bromoperoxidases react with alkenes and alkynes to produce bromochloroderivatives. This same reaction is catalysed when seawater is the source of chloride and bromide ions. This suggests that bromonium ion-induced biosynthesis of chlorinated metabolites occurs in marine environments. The role of iodonium ions in the biosynthesis of chlorinated metabolites is 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.

Enzymatic Halogenation of Allyl Alcohol to 2,3-Bromochloro-, Bromoiodo-, and Fluoroiodo-1-propanols: A Study at the Interface of Chemical and Enzymatic Catalyses

The enzymatic conversion of allyl alcohol to 2,3-bromochloro-, bromoiodo-, and fluoroiodo-l-propanols by various haloperoxidases is reported. This represents the first enzymatic transformation of an unhalogenated organic substrate to heterogeneous dihalide derivatives. Synthesis of the fluoroiodo-compound involves the first reported enzyme-associated fluorination. The mechanism appears to involve the oxidation and incorporation of a halide into allyl alcohol, followed by a non-enzymatic cascade reaction to insert the second and less reactive halide.