Titre and rate constant (kcat/Km) of alkyl hydroperoxide reductase C (AhpC) and steady state H2O2 (hydrogen peroxide) concentration

Range AhpC titre ~5μM: AhpC kcat/Km 4×10^7M^−1×s^−1: H2O2 concentration ~50nM
Organism Bacteria Escherichia coli
Reference Imlay JA. The molecular mechanisms and physiological consequences of oxidative stress: lessons from a model bacterium. Nat Rev Microbiol. 2013 Jul11(7):443-54. doi: 10.1038/nrmicro3032. p.446 Box 2 top paragraphPubMed ID23712352
Primary Source [138] Link, A. J., Robison, K. & Church, G. M. Comparing the predicted and observed properties of proteins encoded in the genome of Escherichia coli K-12. Electrophoresis 18, 1259–1313 (1997). DOI: 10.1002/elps.1150180807 [139] Parsonage, D. et al. Analysis of the link between enzymatic activity and oligomeric state in AhpC, a bacterial peroxiredoxin. Biochemistry 44, 10583–10592 (2005). DOI: 10.1021/bi050448iPubMed ID9298646, 16060667
Method Primary source [138] abstract: "Mining the emerging abundance of microbial genome sequences for hypotheses is an exciting prospect of "functional genomics". At the forefront of this effort, [investigators] compared the predictions of the complete Escherichia coli genomic sequence with the observed gene products by assessing 381 proteins for their mature N-termini, in vivo abundances, isoelectric points, molecular masses, and cellular locations. Two-dimensional gel electrophoresis (2-DE) and Edman sequencing were combined to sequence Coomassie-stained 2-DE spots representing the abundant proteins of wild-type E. coli K-12 strains."
Comments P.446 Box 2 top paragraph: "Does hydrogen peroxide (H2O2) or superoxide (O2−) cause any damage in healthy aerobic Escherichia coli, or has the evolution of scavenging enzymes fully solved the problem? Direct measurements indicate that intracellular H2O2 is formed at a rate of 10 μM/s (BNID 112943). Given the titre (~5 μM) [primary source 138] and rate constant (kcat/Km=4×10^7M^−1×s^−1) [primary source 139] of alkyl hydroperoxide reductase C (AhpC), the primary scavenger, the steady-state H2O2 concentration must be ~50 nM."
Entered by Uri M
ID 112944