cysteinyldopa and 5-hydroxydopa

An analysis of the presence of catechol-derivatives in the sea anemones Metridium senile and Tealia felina, made with the aid of high-pressure liquid chromatography (HPLC), established the presence of dopa, 5-OH-dopa, and 5-S-cysteinyldopa. In addition, 2-S-cysteinyldopa and 2.5-diSS-cysteinyldopa occurred in Metridium. Two unknown substances were found to be present in the tentacles of Metridium and in the tentacles of some specimens of Tealia. Neither catecholamines nor serotonin could be traced in detectable amounts. No dopa-decarboxylase could be demonstrated by the assay performed in this investigation. 6-OH-dopa, 6-OH-dopamine and reserpine had no effect on the formaldehyde-induced fluorescence of the subepithelial tentacular nerve net of Tealia. It is concluded that the tentacular nerve net of sea anemones contains dopa, but neither catecholamines nor serotonin. The localization of the other compounds is not yet established.

Topics: Animals; Cnidaria; Cysteinyldopa; Dihydroxyphenylalanine; Dopa Decarboxylase; Nervous System; Sea Anemones; Species Specificity

The formation of 5-OH-dopa on incubation of tyrosine or dopa with mushroom tyrosinase was studied. Dopa oxidase activity was defined by measuring the formation of 5-S- and 2-S-cysteinyldopa from dopa in the presence of excess amounts of cysteine. This procedure quantitating the immediate nucleophilic reaction products of dopaquinone constitutes a new method for assessing tyrosinase activity. The rate of 5-OH-dopa formation from dopa was similar to that of the formation of dopa from tyrosine. The rate of dopaquinone formation was one order of magnitude higher. When tyrosine was oxidized in the presence of ascorbic acid, 5-OH-dopa formation represented 14% of the original amount of tyrosine. At low concentration of dopa, formation of 5-OH-dopa was proportional to the dopa concentration. At high concentrations the relative quantity of 5-OH-dopa formed decreased. Tyrosine in high concentrations inhibited the formation of 5-OH-dopa from dopa. 5-OH-dopa proved to be a substrate for tyrosinase. The rate of oxidation of 5-OH-dopa was similar to that of dopa. The oxidation products of 5-OH-dopa were transformed into relatively stable fluorophores.

Topics: Basidiomycota; Catechol Oxidase; Chromatography, High Pressure Liquid; Cysteine; Cysteinyldopa; Dihydroxyphenylalanine; Monophenol Monooxygenase; Oxidation-Reduction; Substrate Specificity; Tyrosine

The recently discovered intermediate product in melanin formation, 5-OH-dopa, is formed in large amounts when dopa is oxidized by tyrosinase in the presence of ascorbic acid.

Topics: Ascorbic Acid; Catechol Oxidase; Cysteine; Cysteinyldopa; Dihydroxyphenylalanine; Melanins; Monophenol Monooxygenase; Oxidation-Reduction