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Purification and characterization of enzymes involved in the degradation of chemotactic N-formyl peptides.

N-Formyl peptides are derived from proteolytic degradation/processing of bacterial and mitochondrial proteins and serve as potent chemoattractants for mammalian phagocytic leukocytes. A response to the chemotactic N-formyl peptides released by commensal bacteria in the gut region could be detrimental, leading to unwanted inflammation. Here, two enzymes that act sequentially to degrade N-formyl peptides were purified from the rat intestinal mucosal layer and biochemically characterized. The first enzyme cleaves chemotactic peptide f-MLF to release N-formylmethionine (f-Met) and dipeptide leucylphenylalanine, with a k(cat) value of 14 s(-)(1), a K(M) value of 0.60 mM, and a k(cat)/K(M) value of 22 500 M(-)(1) s(-)(1). In-gel tryptic digestion followed by mass spectral fingerprinting identified the protein as the alpha-N-acylpeptide hydrolase (or acylamino acid-releasing enzyme, EC 3.4.19.1). The second enzyme hydrolyzes N-formylmethionine into formate and methionine with a k(cat) value of 7.9 s(-)(1), a K(M) value of 3.1 mM, and a k(cat)/K(M) value of 2550 M(-)(1) s(-)(1). This protein was identified as the N-acylase IA (or N(alpha)-acyl-l-amino acid amidohydrolase, EC 3.5.1.14). Together, these two enzymes play a protective role in degrading bacterial and mitochondrial N-formylated peptides.