The secondary oxidation of amino-acids by the catechol oxidase of belladonna

The Use of Respiratory Inhibitors

“…Inhibited, light-stable : Polyphenol ox. of potato (8,36), belladonna (145), mushroom (160), and of chloroplast preparations (185); Ascorbic ox. of cueurbits (24 (188).…”

Formation of auxin from tryptophan through action of polyphenols

“…Commercial reagents were used throughout with the exception of 3-nitrocatechol, which was first purified by sublimation in vacuo, mp 59-69 C. quired for the activity of the other phenols, and increased the yield from catechol. The ortho-dihydroxy structure seems to be required for appreciable activity, since resorcinol, tyrosine, o-nitrophenol and o-cresol were ineffective; these compounds also have significantly lower oxidation rates than their o-dihydroxy analogs (22,26). The activity of phenol, pyrogallol, and m-and p-cresol probably derive from their ready conversion by phenolase containing systems to the vicinal dihydroxy analogs (9,30).…”

The oxidation of manganese by peroxidase systems

“…The total 02 outputs were close to theory in all cases (Table 5) It is well known that quinones formed by the action of polyphenol oxidase can bring about secondary oxidations, e.g. coenzyme I (Dixon & Zerfas, 1940), coenzyme II (Kubowitz, 1937), ascorbic acid (Robinson & Nelson, 1944), aminoacids (Happold & Raper, 1925;James, Roberts, Beevers & De Kock, 1948). Evidence has been presented that tyrosinase may act as a terminal oxidase in plant respiration, the quinone acting as a hydrogen acceptor (e.g.…”