title: N-lactoyl-amino acids are ubiquitous metabolites that originate from CNDP2-mediated reverse proteolysis of lactate and amino acids.
abstract: Despite technological advances in metabolomics, large parts of the human metabolome are still unexplored. In an untargeted metabolomics screen aiming to identify substrates of the orphan transporter ATP-binding cassette subfamily C member 5 (ABCC5), we identified a class of mammalian metabolites, N-lactoyl-amino acids. Using parallel protein fractionation in conjunction with shotgun proteomics on fractions containing N-lactoyl-Phe-forming activity, we unexpectedly found that a protease, cytosolic nonspecific dipeptidase 2 (CNDP2), catalyzes their formation. N-lactoyl-amino acids are ubiquitous pseudodipeptides of lactic acid and amino acids that are rapidly formed by reverse proteolysis, a process previously considered to be negligible in vivo. The plasma levels of these metabolites strongly correlate with plasma levels of lactate and amino acid, as shown by increased levels after physical exercise and in patients with phenylketonuria who suffer from elevated Phe levels. Our approach to identify unknown metabolites and their biosynthesis has general applicability in the further exploration of the human metabolome.
authors.affiliation: Divisions of Molecular Oncology.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Jansen
authors.affiliation: Divisions of Molecular Oncology.
authors.forename: Ruben
authors.initials: R
authors.lastname: Addie
authors.affiliation: Cell Biology II, and.
authors.forename: Remco
authors.initials: R
authors.lastname: Merkx
authors.affiliation: Biochemistry, and.
authors.forename: Alexander
authors.initials: A
authors.lastname: Fish
authors.affiliation: Divisions of Molecular Oncology.
authors.forename: Sunny
authors.initials: S
authors.lastname: Mahakena
authors.affiliation: Proteomics Facility, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands; and.
authors.forename: Onno B
authors.initials: OB
authors.lastname: Bleijerveld
authors.affiliation: Proteomics Facility, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands; and.
authors.forename: Maarten
authors.initials: M
authors.lastname: Altelaar
authors.affiliation: Laboratory of Genetic Metabolic Diseases, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Lodewijk
authors.initials: L
authors.lastname: IJlst
authors.affiliation: Laboratory of Genetic Metabolic Diseases, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wanders
authors.affiliation: Divisions of Molecular Oncology.
authors.forename: P
authors.initials: P
authors.lastname: Borst
authors.affiliation: Divisions of Molecular Oncology, k.vd.wetering@nki.nl.
authors.forename: Koen
authors.initials: K
authors.lastname: van de Wetering
mesh_terms: D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004150:Dipeptidases / Q000378:metabolism*; D015444:Exercise / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D007773:Lactates / Q000097:blood / Q000378:metabolism*; D055442:Metabolome; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D059748:Proteolysis
chemical_list: D000596:Amino Acids; D004150:Dipeptidases; D007773:Lactates; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C120809:ABCC5 protein, human; C031499:CNDP2 protein, human
keywords: ABCC5; MRP5; physical exercise; unknown metabolites; untargeted metabolomics