Pseudomonas fluorescens Strain R124 Encodes Three Different MIO Enzymes

Area of Science:

• Biochemistry
• Enzymology
• Microbial Metabolism

Background:

• Class I lyase-like enzymes utilize a 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) catalytic moiety.
• These enzymes include aromatic ammonia-lyases and aromatic 2,3-aminomutases.

Purpose of the Study:

• To investigate the enzymatic repertoire of Pseudomonas fluorescens R124 from a nutrient-limited cave environment.
• To explore novel nitrogen metabolism pathways, including nitrogen fixation and transformation, in response to nitrogen limitation.
• To assess the potential of novel MIO enzymes as biocatalysts for synthesizing enantiopure unnatural amino acids.

Main Methods:

• Isolation and characterization of Pseudomonas fluorescens R124 from a cave.
• Genomic analysis to identify encoded enzymes, including histidine ammonia-lyase, tyrosine/phenylalanine/histidine ammonia-lyase (XAL), and phenylalanine 2,3-aminomutase (PAM).
• Assessment of enzyme properties, such as substrate acceptance and thermal stability, for biocatalytic applications.

Main Results:

• Pseudomonas fluorescens R124 encodes histidine ammonia-lyase, XAL, and PAM.
• The organism demonstrates novel nitrogen fixation and transformation pathways under nitrogen-limited conditions, potentially acquired via horizontal gene transfer of PAM.
• The novel MIO enzymes show promise as biocatalysts for producing enantiopure unnatural amino acids.
• PfXAL exhibits broad substrate acceptance and high thermal stability, making it suitable for biocatalysis.

Conclusions:

• Pseudomonas fluorescens R124 possesses a unique enzymatic profile, including novel MIO enzymes.
• The bacterium has evolved adaptive nitrogen metabolism strategies in nutrient-limited environments.
• The identified enzymes, particularly PfXAL, represent valuable biocatalysts for industrial applications in amino acid synthesis.