Novel activity of Streptomyces aminopeptidase P

Kun Wan,Tadashi Hatanaka,Lingli Yang,Ryota Nakahigashi,Misugi Uraji

doi:10.1186/s40643-020-00309-7

Abstract

Streptomyces aminopeptidase P enzymes are proline-specific peptidases that belong to the peptidase M24 family. To evaluate the activity of a commercial Streptomyces aminopeptidase P, named ‘XPO DUET’, we performed three experiments involving degradation of tryptic casein, production of free amino acids from casein hydrolysate, and hydrolysis of synthetic peptides. Using an ion-trap liquid chromatography–mass spectrometry (LC–MS) apparatus, we demonstrate that XPO DUET could degrade FFVAPFPEVFGK, an allergic and bitter peptide, VAPFPEVFGK, and PEVFGK from tryptic casein. All amino acids, except Ala, Asp, Glu, and Tyr, were released in an XPO DUET activity-dependent manner during the hydrolysis of casein hydrolysate. LC–MS analysis also revealed the ability of XPO DUET to completely hydrolyze Phe-Phe-Phe into free Phe. Thus, we confirm that XPO DUET possesses broader specificity than its known activity toward Xaa-Pro peptides. Because XPO DUET is a food-grade peptidase, it is useful in the bioprocessing of protein hydrolysates through its combination with other food-grade peptidases.

Highlights

Aminopeptidases (APs) are enzymes that catalyze the cleavage of amino acid residues at the N-terminal position of peptides and proteins
After 1 h of treatment with XPO DUET, FFVAPFPEVFGK was scarcely detected with liquid chromatography–mass spectrometry (LC–MS) (Fig. 2b)
After 1 h of treatment with XPO DUET, VAPFPEVFGK was scarcely detected with LC–MS (Fig. 2c), indicating that the enzyme could hydrolyze the N-terminal Val residue of VAPFPEVFGK but not of VLPVPQK

Summary

Introduction

Aminopeptidases (APs) are enzymes that catalyze the cleavage of amino acid residues at the N-terminal position of peptides and proteins. Pro-specific APs include narrow-specificity APs such as prolyl AP, an enzyme that catalyzes the hydrolysis of the N-terminal Pro residue of peptides and proteins. Another example includes aminopeptidase P (APP) that cleaves the N-terminal amino acid residue. Among the 20 naturally occurring amino acids, Pro is unique owing to its unusual cyclic structure. This peculiarity deems Pro residues resistance to hydrolysis by exopeptidases. It was unknown that just one aminopeptidase could degrade various peptides to free amino acids completely

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Discussion

Conclusion