Aminopeptidases Isolated from Cotyledons of Cowpea, Vigna unguiculata

Three aminopeptidases have been separated from cotyledon extractsfrom cowpea, Vigna unguiculata (L.) Walp., and numbered in orderof decreasing affinity for the anion exchange medium DEAE-Sephacel.API showed a wide acceptance of model substrates, with highestactivity under standard conditions against arginyl ß-naphthylamide(NA). AP2 did not act on basic substrates and preferred phenylalanylß-NA. AP3 displayed the narrowest substrate specificity,with strong activity against only alanyl ß-NA andglycyl ß-NA. The chelator 1,10-phenanthroline completelyor almost completely inhibited forms AP1 and AP3, whereas AP2was insensitive to phenanthroline at the same concentration(5 mM). All three aminopeptidases were totally inhibited byAg⁺ or Zn²⁺ ( 0.5 mM). Vigna unguiculata (L.) Walp., aminopeptidase, cotyledon, cowpea, isoenzyme, 1, 10-phenanthroline