Recombinant Lactobacillus helveticus Aminopeptidase E (pepE)
Description
Overview of Key L. helveticus Recombinant Peptidases
The peptidases PepX and PepN from L. helveticus have been extensively studied for their roles in food protein hydrolysis and industrial applications.
Synergistic Hydrolysis of Casein
PepX and PepN exhibit complementary substrate specificities:
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PepN hydrolyzes N-terminal amino acids but is inhibited by proline residues .
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PepX removes X-Pro dipeptides, alleviating PepN inhibition and increasing the degree of hydrolysis by ~132% .
Inhibition Studies
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Substrate Inhibition: Observed in PepN at high substrate concentrations .
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Product Inhibition: Reported for both PepX and PepN during casein hydrolysis .
Recombinant Production and Industrial Relevance
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Expression Levels: PepX and PepN were produced in E. coli with activities 195-fold and 1,000 µkat L⁻¹, respectively, surpassing earlier benchmarks .
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Applications: Used in dairy processing to reduce bitterness and enhance flavor by degrading proline-rich peptides .
Genomic and Proteomic Context
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Gene Clusters: In L. helveticus CNRZ32, pepN, pepX, pepO2, pepV, and pepT are critical for milk protein hydrolysis .
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Regulation: Expression of these peptidases is upregulated in milk, reflecting their role in nutrient acquisition .
Research Gaps and Limitations
No peer-reviewed studies or genomic databases (e.g., UniProt, GenBank) currently describe a pepE gene or "Aminopeptidase E" in L. helveticus. Potential explanations include:
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Nomenclature Variability: "PepE" may refer to a functionally analogous enzyme under a different name.
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Undiscovered Targets: The enzyme might exist in unsequenced strains or require updated annotation efforts.
