Haloperoxidases perhydrolase

Puk O, Huber P, Bischoff D, Recktenwald J, Jung G, Sussmuth RD, van Pee KH, Wohlleben W, Pelzer S. (2002) Glycopeptide biosynthesis in Amycolatopsis mediterranei DSM5908 function of a halogenase and a haloperoxidase/perhydrolase. Chem Biol 9 225-235... 

SCHEME 45.6. Halogenation of monochlorodimedone via metal-free haloperoxidase (perhydrolase). 

Table 16.9-1. FADH2-dependent halogenases, haloperoxidases and perhydrolases used for biotransformation of aromatic compounds and their sources. 

Monochlorodimedone, the substrate used for the detection and isolation of haloperoxidases and perhydrolases (Fig. 16.9-8), and other (3-diketones such as barbituric acid1621 is brominated at the 2-position by all known haloperoxidases and perhydrolases. Oxooctanoic acid and other p-ketoacids form mono- and dihalogen-ated ketones and carbon dioxide1631. When p-alanine and taurine were used as substrates for myeloperoxidase the corresponding N-chloroamines could be detected I64-651. 

Enzymatic halogenation catalyzed by haloperoxidases and perhydrolases involves the oxidation of halide ions to a halonium ion species which leads to the formation of hypohalous acids (Fig. 16.9-1). The products obtained by enzymatic halogenation with these enzymes are the same as the products obtained by chemical electrophilic halogenation with hypohalous acids. The differences in the para ortho ratios in the halogenation of some aromatic compounds could be due to a mixture of halogenation at or near the active site and in solution. 

The major advantage of enzymatic halogenation using haloperoxidases and perhydrolases is that the enzymes have a very low substrate specificity and that no free halogen is needed which makes halogenation catalyzed by these enzymes less hazardous than chemical halogenation. 

Some of the non-heme haloperoxidases and perhydrolases are very stable, even against organic solvents, and easy to use as they do not need any cofactors. However, care has to be taken not to use too high concentrations of hydrogen peroxide, as this could lead to oxidation of the substrate. 

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