Dec 10, 2003

PepN is the major aminopeptidase in Escherichia coli: insights on substrate specificity and role during sodium-salicylate-induced stress

Microbiology
Dilip Chandu, Dipankar Nandi

Abstract

PepN and its homologues are involved in the ATP-independent steps (downstream processing) during cytosolic protein degradation. To obtain insights into the contribution of PepN to the peptidase activity in Escherichia coli, the hydrolysis of a selection of endopeptidase and exopeptidase substrates was studied in extracts of wild-type strains and two pepN mutants, 9218 and DH5alphaDeltapepN. Hydrolysis of three of the seven endopeptidase substrates tested was reduced in both pepN mutants. Similar studies revealed that hydrolysis of 10 of 14 exopeptidase substrates studied was greatly reduced in both pepN mutants. This decreased ability to cleave these substrates is pepN-specific as there is no reduction in the ability to hydrolyse exopeptidase substrates in E. coli mutants lacking other peptidases, pepA, pepB or pepE. PepN overexpression complemented the hydrolysis of the affected exopeptidase substrates. These results suggest that PepN is responsible for the majority of aminopeptidase activity in E. coli. Further in vitro studies with purified PepN revealed a preference to cleave basic and small amino acids as aminopeptidase substrates. Kinetic characterization revealed the aminopeptidase cleavage preference of E. coli PepN to ...Continue Reading

Mentioned in this Paper

Protein Degradation, Regulatory
Bacterial Proteins
Alkalescens-Dispar Group
Amino Acids, I.V. solution additive
Peptide Hydrolases
Cytokinesis of the Fertilized Ovum
Protein Degradation, Metabolic
Aminopeptidase
Endopeptidases
CNDP2 gene

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