The 2-aminoethylphosphonate-specific transaminase of the 2-aminoethylphosphonate degradation pathway

Alexander D. Kim, Angela S. Baker, Debra Dunaway-Mariano, W. W. Metcalf, B. L. Wanner, Brian M. Martin

Research output: Contribution to journalArticlepeer-review


The 2-aminoethylphosphonate transaminase (AEPT; the phnW gene product) of the Salmonella enterica serovar Typhimurium 2-aminoethylphosphonate (AEP) degradation pathway catalyzes the reversible reaction of AEP and pyruvate to form phosphonoacetaldehyde (P-Ald) and L-alanine (L-Ala). Here, we describe the purification and characterization of recombinant AEPT. pH rate profiles (log Vm and log Vm/Km versus pH) revealed a pH optimum of 8.5. At pH 8.5, Keq is equal to 0.5 and the kcat values of the forward and reverse reactions are 7 and 9 s-1, respectively. The Km for AEP is 1.11 ± 0.03 mM; for pyruvate it is 0.15 ± 0.02 mM, for P-Ald it is 0.09 ± 0.01 mM, and for L-Ala it is 1.4 ± 0.03 mM. Substrate specificity tests revealed a high degree of discrimination, indicating a singular physiological role for the transaminase in AEP degradation. The 40-kDa subunit of the homodimeric enzyme is homologous to other members of the pyridoxalphosphate-dependent amino acid transaminase superfamily. Catalytic residues conserved within well-characterized members are also conserved within the seven known AEPT sequences. Site-directed mutagenesis demonstrated the importance of three selected residues (Asp168, Lys194, and Arg340) in AEPT catalysis.

Original languageEnglish (US)
Pages (from-to)4134-4140
Number of pages7
JournalJournal of bacteriology
Issue number15
StatePublished - 2002
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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