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Stereochemistry and mechanism of a microbial phenylalanine aminomutase

Nishanka Dilini Ratnayake1, Udayanga Wanninayake, James H Geiger

  • 1Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.

Journal of the American Chemical Society
|May 13, 2011
PubMed

Insights

The stereochemistry of phenylalanine aminomutase (PAM) from Pantoea agglomerans (Pa) was investigated. This enzyme isomerizes α-phenylalanine to β-phenylalanine with inversion of configuration, unlike related enzymes.

Area of Science:

  • Biochemistry
  • Enzymology
  • Organic Chemistry

Background:

  • Phenylalanine aminomutase (PAM) enzymes are crucial in biosynthesis.
  • The andrimid pathway in Pantoea agglomerans utilizes a specific PAM (PaPAM).
  • PaPAM belongs to the 4-methylidene-1H-imidazol-5(4H)-one (MIO)-dependent enzyme family.

Purpose of the Study:

  • To elucidate the stereochemical mechanism of PaPAM.
  • To compare the catalytic mechanism of PaPAM with other known aminomutases.

Main Methods:

  • Stereochemical analysis of the enzymatic reaction.
  • Mechanistic studies of MIO-dependent catalysis.

Main Results:

  • PaPAM catalyzes the isomerization of (2S)-α-phenylalanine to (3S)-β-phenylalanine.
  • The reaction proceeds via complete intramolecular removal and interchange of the NH(2) and pro-(3S) hydrogen groups.
  • A key finding is the inversion of configuration at the migration centers during β-phenylalanine formation.

Conclusions:

  • PaPAM employs a distinct stereochemical pathway compared to TcPAM from Taxus plants.
  • The observed inversion mechanism provides new insights into MIO-dependent aminomutase catalysis.

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