A remarkable activity of human leukotriene A4 hydrolase (LTA4H) toward unnatural amino acids

Amino Acids. 2014 May;46(5):1313-20. doi: 10.1007/s00726-014-1694-2. Epub 2014 Feb 27.

Abstract

Leukotriene A4 hydrolase (LTA4H--EC 3.3.2.6) is a bifunctional zinc metalloenzyme, which processes LTA4 through an epoxide hydrolase activity and is also able to trim one amino acid at a time from N-terminal peptidic substrates via its aminopeptidase activity. In this report, we have utilized a library of 130 individual proteinogenic and unnatural amino acid fluorogenic substrates to determine the aminopeptidase specificity of this enzyme. We have found that the best proteinogenic amino acid recognized by LTA4H is arginine. However, we have also observed several unnatural amino acids, which were significantly better in terms of cleavage rate (k cat/K m values). Among them, the benzyl ester of aspartic acid exhibited a k cat/K m value that was more than two orders of magnitude higher (1.75 × 10(5) M(-1) s(-1)) as compared to L-Arg (1.5 × 10(3) M(-1) s(-1)). This information can be used for design of potent inhibitors of this enzyme, but may also suggest yet undiscovered functions or specificities of LTA4H.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism*
  • Arginine / metabolism
  • Binding Sites
  • Epoxide Hydrolases / chemistry*
  • Epoxide Hydrolases / genetics
  • Epoxide Hydrolases / metabolism*
  • Humans
  • Kinetics
  • Substrate Specificity

Substances

  • Amino Acids
  • Arginine
  • Epoxide Hydrolases
  • leukotriene A4 hydrolase