Deamidase inactivates a D-amino acid-containing Aplysia neuropeptide.
Membrane-catalyzed degradation of the cardioexcitatory peptide, Asn-D-Trp-Phe-NH(2) (N(d)WF-NH(2)), which was previously isolated from Aplysia, was investigated in relation to its inactivation mechanism. The principal degradation was deamidation of the C-terminal amide, producing biologically inert Asn-D-Trp-Phe-OH (N(d)WF-OH). Among membrane fractions prepared from different organs, the fraction from the ganglia showed the highest specific activity of the deamidation reaction. The deamidase activity was inhibited by Ebelactone B and the serine protease inhibitor, phenylmethanesulfonyl fluoride (PMSF), while the degradation of the synthetic stereoisomer, Asn-Trp-Phe-NH(2) (N(l)WF-NH(2)), was sensitive to the divalent cation-chelating agent, o-phenanthroline, and aminopeptidase inhibitors, amastatin and bestatin. The presence of D-Trp residue in the second position of N(d)WF-NH(2) endows this peptide not only with stereospecific bioactivity but also peptidase stability. The deamidation reaction seems to be the major inactivation mechanism for this peptide.
Morishita
F
F
Department of Biological Science, Faculty of Science, Hiroshima University, Higashi Hiroshima 739-8526, Japan.
Matsushima
O
O
Furukawa
Y
Y
Minakata
H
H
D000581:Amidohydrolases / Q000378:metabolism*; D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D001048:Aplysia; D009479:Neuropeptides / Q000037:antagonists & inhibitors* / Q000737:chemistry
D000596:Amino Acids; D009479:Neuropeptides; D000581:Amidohydrolases