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Related Experiment Videos

Utilization of dipeptides by Lactococcus lactis ssp. cremoris.

A van Boven1, W N Konings

  • 1Department of Microbiology, University of Groningen, Haren, The Netherlands.

Biochimie
|April 1, 1988
PubMed
Summary

Peptide uptake, not hydrolysis, limits Lactococcus lactis peptide breakdown. Growth rates depend on available amino acids, not intracellular enzyme activity.

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Lactococcus lactis ssp. cremoris is crucial in dairy fermentation.
  • Peptide hydrolysis is vital for amino acid availability.
  • Strain-specific differences in peptide hydrolysis exist.

Purpose of the Study:

  • Investigate the rate-limiting step in peptide hydrolysis by Lactococcus lactis ssp. cremoris.
  • Determine factors influencing amino acid uptake and utilization.
  • Examine the regulation of protease and peptidase synthesis.

Main Methods:

  • Comparing peptide hydrolysis rates in whole cells versus cell-free extracts.
  • Assessing competitive inhibition of dipeptide utilization.
  • Analyzing amino acid release, accumulation, and incorporation.
  • Measuring intracellular peptidase activity and peptide uptake rates.

Main Results:

  • Peptide uptake, not hydrolysis, is the rate-limiting step.
  • Structurally similar dipeptides competitively inhibit uptake.
  • Hydrolyzed amino acids are mostly released, with minimal accumulation/incorporation.
  • Protease and peptidase synthesis are regulated independently.
  • Growth rate correlates with external amino acid availability, not intracellular enzyme levels.

Conclusions:

  • Peptide transport is a key regulatory point for amino acid acquisition in Lactococcus lactis.
  • Amino acid availability in the environment dictates growth, overriding intracellular enzyme capacity.
  • Differential regulation of proteases and peptidases suggests distinct physiological roles.

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