The Chemical Basis of Serine Palmitoyltransferase Inhibition by Myriocin.Wadsworth, J.M., Clarke, D.J., Mcmahon, S.A., Lowther, J.P., Beattie, A.E., Langridge-Smith, P.R.R., Broughton, H.B., Dunn, T.M., Naismith, J.H., Campopiano, D.J.
(2013) J.Am.Chem.Soc. 135: 14276
- PubMed: 23957439
- DOI: 10.1021/ja4059876
- PubMed Abstract:
Sphingolipids (SLs) are essential components of cellular membranes formed from the condensation of L-serine and a long-chain acyl thioester. This first step is catalyzed by the pyridoxal-5'-phosphate (PLP)-dependent enzyme serine palmitoyltransferase ...
Sphingolipids (SLs) are essential components of cellular membranes formed from the condensation of L-serine and a long-chain acyl thioester. This first step is catalyzed by the pyridoxal-5'-phosphate (PLP)-dependent enzyme serine palmitoyltransferase (SPT) which is a promising therapeutic target. The fungal natural product myriocin is a potent inhibitor of SPT and is widely used to block SL biosynthesis despite a lack of a detailed understanding of its molecular mechanism. By combining spectroscopy, mass spectrometry, X-ray crystallography, and kinetics, we have characterized the molecular details of SPT inhibition by myriocin. Myriocin initially forms an external aldimine with PLP at the active site, and a structure of the resulting co-complex explains its nanomolar affinity for the enzyme. This co-complex then catalytically degrades via an unexpected 'retro-aldol-like' cleavage mechanism to a C18 aldehyde which in turn acts as a suicide inhibitor of SPT by covalent modification of the essential catalytic lysine. This surprising dual mechanism of inhibition rationalizes the extraordinary potency and longevity of myriocin inhibition.
School of Chemistry, The University of Edinburgh , Edinburgh, Scotland, EH9 3JJ, United Kingdom.