Subunit structured of pig small-intestinal brush-border aminopeptidase N

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Abstract
Aminopeptidase N (EC 3.4.11.2), when isolated from pig intestine in the proteinase- or detergent-released form, frequently appears to contain 3 polypeptide chains, here termed .alpha., .beta. and .gamma.. An immunological technique established that the .beta.- and .gamma.-polypeptides are derived from the .alpha.-chain and that the intact enzyme is a dimer, .alpha.2. Each .alpha.-chain of the detergent form was shown to contain a hydrophobic anchor peptide about 35 amino acid residues in length, which included the N-terminal sequence. A peptide bond in the .alpha.-chain was very sensitive to proteolysis. Its cleavage generated the commonly observed forms: .alpha..beta..gamma. and .beta.2.gamma.2. The .gamma.-fragment, which lacked the anchor peptide, was derived from the C-terminal part of the .alpha.-chain.