Studies on the enzyme that catalyzes D/L-isomerization of an amino acid during the post-translational modification of neuropeptide precursor.

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NdWFamide (NdWFa) is a D-amino acid containing neuropeptide of the marine gastropod, Aplysia kurodai. In this study, we attempt to identify the peptidyl D/L-isomerase (PI) that catalyzes the D-/L-conversion of NdWFa in Aplysia. To this end, we prepared NdWFa-expressing neuron specific cDNAs by the subtraction method. When the cDNAs were cloned and sequenced, we found that several predicted proteins with N-terminal signal peptide could not be specified their functions by homology search on database. We currently assume that those proteins are candidates for the PI of Aplysia.Then, we tried to establish NdWFa-expressing cell-line, because such cells could be used for the bioassay system for the candidate genes of the PI. Transformation of NdWFa-precursor gene to CHO-K1 cell seems to be successful. However, biosynthesis of the peptide could not be confirmed, so far. We may need fine-tuning of experimental conditions that leads to more effective expression of foreign gene.