naag synthetase activity mediates the biosynthesis of naag from glutamate and naa, but little is known about the mechanism or regulation of this enzyme, and no naag synthetase activity has been isolated in cell-free preparations. since other neuropeptides and nearly all vertebrate peptides are synthesized by post-translational processing, naag synthtase activity is relatively unique. as with naa, the synthesis of naag is primarily restricted to neurons, although glial cells also contain and synthesize this peptide. in vitro, naag synthesis appears to be regulated by the availability of its precursor, naa. in addition, during differentiation of neuroblastoma cells, it has been shown that a protein kinase a (pka) activator will increase the quantity of naag, while a protein kinase c (pkc) activator will decrease its concentration. this finding suggests that pka and pkc have opposing regulatory effects on the naag synthetase enzyme.