Bilirubin derivatives, polymers

Gallstones occasionally contain black pigments which consist of polymers of bilirubin derivatives. To study whether any bile pigment metal complex is also... 

A different type of polypeptide has been made by polymerizing tyrosine and its derivatives with peroxidase, laccase, or bilirubin oxidase [19, 63], The resulting polymers do not have the a-peptide structure, but consist of polyphenols with mixtures of phenylene and oxyphenylene units. Tyranosinase is also known to oxidize tyrosine, which can lead to polymerization reactions to form melanin [64]. 

In living cells, various oxidoreductases play an important role in maintaining the metabolism of living systems. So far, peroxidase containing Fe-active site, laccase containing Cu-active site, tyrosinase (polyphenol oxidase, Cu-active site), bilirubin oxidase (Cu-active site), etc, have been reported to act as catalyst for oxidative polymerization of phenol and aniline derivatives and for polymer modification via oxidative coupling. 

Deglycosylation of the polyarbutin gave poly(l,4-dihydroxy-2,6-phenylene). This polymer was different from the electrochemically synthesised polyhydroquinone, which is poly(l,4-dihydroxy-2,5-phenylene). Kobayashi and co-workers [194] synthesised a new kind of polyhydroquinone derivative with a mixture of phenylene and oxyphenylene units using peroxidases (horseradish and soybean) to catalyse the polymerisation of 4-hydroxyphenyl benzoate and the snbsequent hydrolysis of the resulting polymer (Scheme 12.18). Similarly, Tripathy and co-workers [195] synthesised a photoactive azopolymer, poly(4-phenylazophenol), via HRP-catalysed polymerisation in acetone and sodium phosphate buffer bilirubin oxidase (EC 1.3.3.5) was shown to catalyse the regioselective polymerisation of 1,5-dihydroxynaphthalene to a polymer in a mixed solvent composed of dioxane, ethylacetate and acetate buffer [196]. 

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