70 – Aminopeptidase Ey

Publisher Summary This chapter describes the structural chemistry and the biological aspects of aminopeptidase Ey. The introduction of a sensitive fluorogenic substrate, Leu-NHMec, and a chromogenic substrate, Leu-NHPhNO2, at pH 7.5 led to the discovery of aminopeptidase Ey in hen's egg yolk. The enzyme has a broad specificity for N-terminal amino acid residues at the P1 position. Aminopeptidase Ey has a broad specificity for amino acid residues at the P1 position of substrates. The enzyme degrades a variety of peptides having various N-terminal amino acids: hydrophobic, basic and acidic amino acids including proline. Aminopeptidase Ey is a dimeric enzyme with homologous subunits, each having a molecular mass of 150,000 Da. It contains 1.0 mol of zinc per mol of each subunit. The enzyme molecule is seen as a dimer composed of two globular subunits by electron micrography at a magnification of 100,000×. The pI of the enzyme is about 2.8 as determined by isoelectric focusing. An asialo form of the enzyme, obtained by treatment with Arthrobacter sialidase, has a pI of 4.4.