A New Microbial Pathway for Organophosphonate Degradation Catalyzed by Two Previously Misannotated Non-Heme-Iron Oxygenases

Journal Article · Thu Feb 21 04:00:00 UTC 2019 · Biochemistry

DOI: https://doi.org/10.1021/acs.biochem.9b00044 · OSTI ID:1513018

Rajakovich, Lauren J.  ^[1]; Pandelia, Maria-Eirini ^[2]; Mitchell, Andrew J. ^[3]; Chang, Wei-chen  ^[4]; Zhang, Bo ^[5]; Boal, Amie K.  ^[6]; Krebs, Carsten  ^[6]; Bollinger, J. Martin  ^[6]

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1. Pennsylvania State Univ., University Park, PA (United States); Harvard Univ., Cambridge, MA (United States)
2. Pennsylvania State Univ., University Park, PA (United States); Brandeis Univ., Waltham, MA (United States)
3. Pennsylvania State Univ., University Park, PA (United States); Whitehead Institute for Biomedical Research, Cambridge, MA (United States)
4. Pennsylvania State Univ., University Park, PA (United States); North Carolina State Univ., Raleigh, NC (United States)
5. Pennsylvania State Univ., University Park, PA (United States); REG Life Sciences, LLC, South San Francisco, CA (United States)
6. Pennsylvania State Univ., University Park, PA (United States)

The assignment of biochemical functions to hypothetical proteins is challenged by functional diversification within many protein structural superfamilies. This diversification, which is particularly common for metalloenzymes, renders functional annotations that are founded solely on sequence and domain similarities unreliable and often erroneous. Definitive biochemical characterization to delineate functional subgroups within these superfamilies will aid in improving bioinformatic approaches for functional annotation. We describe here the structural and functional characterization of two non-heme-iron oxygenases, TmpA and TmpB, which are encoded by a genomically clustered pair of genes found in more than 350 species of bacteria. TmpA and TmpB are functional homologues of a pair of enzymes (PhnY and PhnZ) that degrade 2-aminoethylphosphonate but instead act on its naturally occurring, quaternary ammonium analogue, 2-(trimethylammonio)ethylphosphonate (TMAEP). TmpA, an iron(II)- and 2-(oxo)glutarate-dependent oxygenase misannotated as a γ-butyrobetaine (γbb) hydroxylase, shows no activity toward γbb but efficiently hydroxylates TMAEP. The product, (R)-1-hydroxy-2-(trimethylammonio)ethylphosphonate [(R)-OH-TMAEP], then serves as the substrate for the second enzyme, TmpB. By contrast to its purported phosphohydrolytic activity, TmpB is an HD-domain oxygenase that uses a mixed-valent diiron cofactor to enact oxidative cleavage of the C–P bond of its substrate, yielding glycine betaine and phosphate. The high specificities of TmpA and TmpB for their N-trimethylated substrates suggest that they have evolved specifically to degrade TMAEP, which was not previously known to be subject to microbial catabolism. Here, this study thus adds to the growing list of known pathways through which microbes break down organophosphonates to harvest phosphorus, carbon, and nitrogen in nutrient-limited niches.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: National Science Foundation (NSF); National Institutes of Health (NIH); Michigan Economic Development Corp.; USDOE Office of Science (SC)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1513018
• Journal Information: Biochemistry, Journal Name: Biochemistry Journal Issue: 12 Vol. 58; ISSN 0006-2960
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: ENGLISH