High-performance liquid chromatographic procedure for the simultaneous determination of aromatic L-amino acid decarboxylase activity towards 3,4-dihydroxyphenylalanine and 5-hydroxytryptophan.
A high-performance liquid chromatographic method with electrochemical detection has been developed and applied in the simultaneous determination of aromatic L-amino acid decarboxylase activity with respect to L-3,4-dihydroxyphenylalanine and 5-hydroxytryptophan as substrates. Both substrates are included in the incubation mixture, and the decarboxylated products, dopamine and serotonin, respectively, are detected. In contrast to several earlier claims, we found that the ratio of the decarboxylase activity to L-3,4-dihydroxyphenylalanine and 5-hydroxytryptophan is quite constant across several different rat tissues, supporting the notion that there is only one major single enzyme rather than two. We also observed that an erroneous ratio with respect to the L-3,4-dihydroxyphenylalanine/5-hydroxytryptophan decarboxylation activities, is obtained if these activities are assessed under non-linear kinetic conditions.
Department of Psychiatry, University of Saskatchewan, Saskatoon, Canada.
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D006916:5-Hydroxytryptophan / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000032:analysis / Q000276:immunology; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D066298:In Vitro Techniques; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism*; D008297:Male; D011506:Proteins / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains
D000911:Antibodies, Monoclonal; D011506:Proteins; D007980:Levodopa; D006916:5-Hydroxytryptophan; D001142:Aromatic-L-Amino-Acid Decarboxylases