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A procedure for the purification of smallcap˜L-DOPA decarboxylase (DDC) from the white puparia of the tephritid Ceratitis capitata is described. Polyacrylamide gel electrophoresis (PAGE) in the presence or absence of sodium dodecyl sulfate (SDS) revealed the homogeneity of the final preparation. The enzyme molecular weight determined by gel filtration was about 100 000 dalton. A single band appeared on SDS-PAGE of a molecular weight estimated at about 48 000. Therefore a dimeric structure is proposed for the DDC molecule from C. capitata. The enzyme exhibited a remarkable specificity only towards smallcap˜L-DOPA and none of the ions tested had either a strong inhibitory or stimulatory effect on enzyme activity.