Isolation of NPY-25 (neuropeptide Y[12-36]), a potent inhibitor of calmodulin, from porcine brain.

In the present purification of low molecular weight fractions (Mr: 2000-4000) containing basic peptides, twenty nmol of novel calmodulin binding peptide, possessing a potent affinity for calmodulin, was isolated from 18 kg of porcine brain. By analysis with gas phase sequencer, the sequence was determined to be APAEDLARYYSALRHYINLITRQRY. Carboxy terminus of the peptide was determined to be Tyr-NH2. The peptide was a carboxy terminal pentacosanepeptide of neuropeptide Y and was termed NPY-25. NPY-25 competitively inhibited the activation of cAMP-phosphodiesterase through CaM binding in a Ca++ dependent fashion, but did not inhibit the basal activity of cAMP phosphodiesterase. NPY-25 elicited a more potent activity than did neuropeptide Y. IC50 values of NPY-25 and Neuropeptide Y were 0.06 microM and 0.54 microM respectively.