2. Academic Validation
  3. The metalloprotein YhcH is an anomerase providing N-acetylneuraminate aldolase with the open form of its substrate

The metalloprotein YhcH is an anomerase providing N-acetylneuraminate aldolase with the open form of its substrate

  • J Biol Chem. 2021 Jan-Jun;296:100699. doi: 10.1016/j.jbc.2021.100699.
Takfarinas Kentache 1,  Leopold Thabault 2,  Gladys Deumer 3,  Vincent Haufroid 3,  Raphaël Frédérick 2,  Carole L Linster 4,  Alessio Peracchi 5,  Maria Veiga-da-Cunha 1,  Guido T Bommer 6,  Emile Van Schaftingen 7
Affiliations

Affiliations

  • 1 Laboratory of Physiological Chemistry, de Duve Institute, UCLouvain, Brussels, Belgium.
  • 2 Medicinal Chemistry Research Group (CMFA), Louvain Drug Research Institute (LDRI), UCLouvain, Brussels, Belgium.
  • 3 Louvain Center for Toxicology and Applied Pharmacology, UCLouvain, Brussels, Belgium.
  • 4 Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Belvaux, Luxembourg.
  • 5 Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy.
  • 6 Laboratory of Physiological Chemistry, de Duve Institute, UCLouvain, Brussels, Belgium; Walloon Excellence in Life Sciences and Biotechnology (WELBIO), UCLouvain, Brussels, Belgium.
  • 7 Laboratory of Physiological Chemistry, de Duve Institute, UCLouvain, Brussels, Belgium. Electronic address: [email protected].
PMID: 33895133 DOI: 10.1016/j.jbc.2021.100699
Abstract

N-acetylneuraminate (Neu5Ac), an abundant sugar present in glycans in vertebrates and some bacteria, can be used as an energy source by several prokaryotes, including Escherichia coli. In solution, more than 99% of Neu5Ac is in cyclic form (≈92% beta-anomer and ≈7% alpha-anomer), whereas <0.5% is in the open form. The aldolase that initiates Neu5Ac metabolism in E. coli, NanA, has been reported to act on the alpha-anomer. Surprisingly, when we performed this reaction at pH 6 to minimize spontaneous anomerization, we found NanA and its human homolog NPL preferentially metabolize the open form of this substrate. We tested whether the E. coli Neu5Ac anomerase NanM could promote turnover, finding it stimulated the utilization of both beta and alpha-anomers by NanA in vitro. However, NanM is localized in the periplasmic space and cannot facilitate Neu5Ac metabolism by NanA in the cytoplasm in vivo. We discovered that YhcH, a cytoplasmic protein encoded by many Neu5Ac catabolic operons and belonging to a protein family of unknown function (DUF386), also facilitated Neu5Ac utilization by NanA and NPL and displayed Neu5Ac anomerase activity in vitro. YhcH contains Zn, and its accelerating effect on the aldolase reaction was inhibited by metal chelators. Remarkably, several transition metals accelerated Neu5Ac anomerization in the absence of Enzyme. Experiments with E. coli mutants indicated that YhcH expression provides a selective advantage for growth on Neu5Ac. In conclusion, YhcH plays the unprecedented role of providing an aldolase with the preferred unstable open form of its substrate.

Keywords

aldolase; anomerase; metalloprotein; mutarotase; sialic acid.

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