Elucidating the chemical structure of native 1-deoxysphingosine

  • J Lipid Res. 2016 Jul;57(7):1194-203. doi: 10.1194/jlr.M067033.
Regula Steiner  1 ,  Essa M Saied  2 ,  Alaa Othman  1 ,  Christoph Arenz  2 ,  Alan T Maccarone  3 ,  Berwyck L J Poad  4 ,  Stephen J Blanksby  4 ,  Arnold von Eckardstein  1 ,  Thorsten Hornemann  5
Affiliations
  • 1. Institute of Clinical Chemistry, University and University Hospital of Zurich, CH-8091 Zurich, Switzerland.
  • 2. Institute for Chemistry, Humboldt Universität zu Berlin, 12489 Berlin, Germany; Chemistry Department, Faculty of Science, Suez Canal University, Ismailia, Egypt.
  • 3. Mass Spectrometry User Resource and Research Facility, School of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia.
  • 4. Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4001, Australia.
  • 5. Institute of Clinical Chemistry, University and University Hospital of Zurich, CH-8091 Zurich, Switzerland [email protected].
PMID: 27165858 DOI: 10.1194/jlr.M067033
Abstract

The 1-deoxysphingolipids (1-deoxySLs) are formed by an alternate substrate usage of the enzyme, serine-palmitoyltransferase, and are devoid of the C1-OH-group present in canonical Sphingolipids. Pathologically elevated 1-deoxySL levels are associated with the rare inherited neuropathy, HSAN1, and diabetes type 2 and might contribute to β cell failure and the diabetic sensory neuropathy. In analogy to canonical Sphingolipids, it was assumed that 1-deoxySLs also bear a (4E) double bond, which is normally introduced by sphingolipid delta(4)-desaturase 1. This, however, was never confirmed. We therefore supplemented HEK293 cells with isotope-labeled D3-1-deoxysphinganine and compared the downstream formed D3-1-deoxysphingosine (1-deoxySO) to a commercial synthetic SPH m18:1(4E)(3OH) standard. Both compounds showed the same m/z, but differed in their RPLC retention time and atmospheric pressure chemical ionization in-source fragmentation, suggesting that the two compounds are structural isomers. Using dimethyl disulfide derivatization followed by MS(2) as well as differential-mobility spectrometry combined with ozone-induced dissociation MS, we identified the carbon-carbon double bond in native 1-deoxySO to be located at the (Δ14) position. Comparing the chromatographic behavior of native 1-deoxySO to chemically synthesized SPH m18:1(14Z) and (14E) stereoisomers assigned the native compound to be SPH m18:1(14Z). This indicates that 1-deoxySLs are metabolized differently than canonical Sphingolipids.

Keywords
deoxysphingolipids; differential-mobility spectrometry; dimethyl disulfide adducts; double bond position; mass spectrometry; ozone-induced dissociation; structural isomers.
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