title: The chemical basis of serine palmitoyltransferase inhibition by myriocin.
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 (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.
authors: School of Chemistry, The University of Edinburgh , Edinburgh, Scotland, EH9 3JJ, United Kingdom.
authors: John M
authors: JM
authors: Wadsworth
authors: David J
authors: DJ
authors: Clarke
authors: Stephen A
authors: SA
authors: McMahon
authors: Jonathan P
authors: JP
authors: Lowther
authors: Ashley E
authors: AE
authors: Beattie
authors: Pat R R
authors: PR
authors: Langridge-Smith
authors: Howard B
authors: HB
authors: Broughton
authors: Teresa M
authors: TM
authors: Dunn
authors: James H
authors: JH
authors: Naismith
authors: Dominic J
authors: DJ
authors: Campopiano
mesh_terms: D018360:Crystallography, X-Ray; D005229:Fatty Acids, Monounsaturated / Q000737:chemistry*; D007700:Kinetics; D009154:Mutation; D011994:Recombinant Proteins / Q000737:chemistry; D051102:Serine C-Palmitoyltransferase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D020578:Sphingomonas / Q000201:enzymology / Q000235:genetics
chemical_list: D005229:Fatty Acids, Monounsaturated; D011994:Recombinant Proteins; D051102:Serine C-Palmitoyltransferase; C001996:thermozymocidin