Synthesis of L-[β-11C]amino acids using immobilized enzymes

L-[beta-C-11]-3,4-dihydroxyphenylalanine (L-[beta-C-11]DOPA) and L-[beta-C-11]-5-hydroxytryptophan(L-[beta-C-11]-5-HTP) were synthesized in one step with immobilized thermostable enzymes (alanine racemase, D-amino acid oxidase, and beta-tyrosinase or tryptophanase) on an aminopropyl-CPG carrier in a single column and by passing D,L-[3-C-11]alanine through the column with coenzymes and other substrates. L-[beta-C-11]DOPA and L-[beta-C-11]-5-HTP could be obtained at yields of 53% and 60%, respectively, by optimizing the amounts and the ratios of the enzymes used, the reaction temperature, the pH, and the flow rate. Moreover, the same immobilized enzyme column could be used repeatedly. (C) 1999 Elsevier Science Ltd. All rights reserved.