Purification and characterization of porcine skeletal muscle aminopeptidase T, a novel metallopeptidase homologous to leukotriene A4 hydrolase

A novel aminopeptidase, Aminopeptidase T (APase T), was purified from porcine skeletal muscle following successive column chromatography: twice on DEAE-cellulose, hydroxyapatite, and Sephacryl S-200 HR using Leu-β-naphthylamide (LeuNap) as a substrate. The molecular mass of the enzyme was 69 kDa on SDS-PAGE. The optimum pH towards LeuNap of the enzyme was about 7. The enzyme activity was strongly inhibited by bestatin and was negatively affected by ethylenediaminetetraacetic acid (EDTA). Chlorine-activated APase T liberated Leu, Ala, Met, Pro, and Arg from Nap derivatives. The APase T gene consisted of an ORF of 1,836 bp encoding a protein of 611 amino acid residues. The APase T was highly homologous to bovine, human, and mouse Leukotriene A(4) hydrolase (LTA(4)H), a bifunctional enzyme which exhibits APase and epoxide hydrolase activity.