Thiolperoxidase

Oxidation of thiols and related compounds with organoselenium(IV) and organotellurium(rV) compounds 102 Other oxidations with selenoxides and telluroxides 106 Thiolperoxidase and haloperoxidase-like activity of organoselenides and organotellurides 108... 

THIOLPEROXIDASE AND HALOPEROXIDASE-LIKE ACTIVITY OF ORGANOSELENIDES AND ORG ANOTET. 1.1 JRIDF..S... 

The catalytic cycle for the thiolperoxidase and haloperoxidase-like activity of diorganoselenides and tellurides is summarized in Fig. 25. Stopped-flow spectroscopy has been used to elicit mechanistic details of the cycle. " " Following oxidation to the selenoxide or telluroxide, the catalytic cycle for thiolperoxidase-like activity is shown in Fig. 21. The details of the haloperoxidase-like cycle are not as well defined. Using dihydroxytellurane 52 as a substrate, the addition of 0.5 M sodium iodide in pH 6.8 buffer gave a fast reaction with a second-... 

Fig. 25 A summary of haloperoxidase-like and thiolperoxidase-like reactions of diorganoselenides and tellurides.

The dendrimer wedges with two, three, and four organotelluride groups and the first-generation Frechet-type dendrimers based on 3,5-dihydroxybenzyl alcohol and l,l,l-tris-4-hydroxyphenylethane shown in Fig. 26 illustrate statistical effects in thiolperoxidase-like reactions. Nearly linear increases in reactivity on a molar basis with increasing numbers of organotelluride groups were observed in the oxidation of... 

Fig. 26 Dendrimer wedges and first-generation dendrimers that have been used as catalysts with hydrogen peroxide in thiolperoxidase- and haloperoxidase-like reactions.

Table 5 Thiolperoxidase-like behavior of tnonotellurides 60, dendrimer wedges 61-63, and dendrimers 64 toward the oxidation of thiophenol with hydrogen peroxide in methanol...

Diorgano diselenides have been used extensively as precursors to seleninic acids in the presence of hydrogen peroxide.The catalytic activity of preformed seleninic acids and seleninic acids generated in situ are identical. Diorgano ditellurides have also been used as catalysts in thiolperoxidase-like reactions for the oxidation of thiols with various peroxides. However, tellurinic acids are not thought to be involved even though RTe(=0)SPh types of structures are proposed as intermediates. 

Water-soluble diorganyl tellurides with thiolperoxidase and autoxidant activity have been prepared as depicted in the following scheme. ... 

---