The Chemical Mechanism of The Oxidative Deamination of Amino Acids by Catechol and PolYPHENOLASE

Abstract

SummaryThe continuous deamination of certain amino acids by the system catecholpolyphenolase takes place through intensely coloured intermediate compounds. These intermediates are formed by the combination of equimolecular proportions of o-quinone with amino acids or secondary amines. They are presented as structural homologues of adrenochrome or hallachrome and probably of Szent-Gyorgyi's tyrin (1925).It is suggested that the continuous deamination is brought about through condensation of the colour compound with one further molecule of ~ suitable amino acid and rearrangement and hydrolysis into keto acid and substituted amino phenol. It is supposed that the latter is re-oxidized with liberation of ammQnia and regeneration of the o-quinonoid colour compound. A formulation of the chemical mechanism is tentatively proposed and individual steps of the reaction are compared with observations made in the oxidation of amino acids by other polyketo compounds . like alloxan and isatin. The conditiOns and limitations of the reaction are discussed.

Studies on the Biosynthesis of Ergot Alkaloids

“…The only other inajor pathway b y which tryptophan is metabolized appears to be the formation of a red-brown pign~ent. This is believed to be ol the type generated by the action of polyphenoloxidase upon phenolic compounds in the presence of amino acids or proteins (22). The incorporation of Cl4-labelled phenylalanine and tyrosine a s well as tryptophan into the piginent provides support for this belief.…”

Formation of auxin from tryptophan through action of polyphenols

“…Their effectiveness indicates that the nature of the para substituent is not highly specific, a characteristic consistent with the inference that a p-substitution stabilizes the o-quinoid structure through repeated oxidations and reduction (39). Ap Benzoquinone was synthesized by the silver-oxide oxidation of catechol, using the method described by Tarpley (38).…”

The Precursors of Chocolate Aroma: A Comparative Study of Fermented and Unfermented Cocoa Beans

“…Although the relative importance of the three principal precursor groups is yet to be settled, their nature suggests that the operative reaction in the development of chocolate aroma might be a Strecker degradation of the amino acid fraction. This could occur through the agency of the flavonoids (Jackson and Kendall, 1949;Trautner and Roberts, 1950;Isherwood and Niavis, 1956).…”