Details

Autor(en) / Beteiligte

• Chatterjee, Abhishek
• Abeydeera, N. Dinuka
• Bale, Shridhar
• Pai, Pei-Jing
• Dorrestein, Pieter C.
• Russell, David H.
• Ealick, Steven E.
• Begley, Tadhg P.

Titel

Saccharomyces cerevisiae THI4p is a suicide thiamine thiazole synthase

Ist Teil von

• Nature (London), 2011-10, Vol.478 (7370), p.542-546

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2011

Quelle

MEDLINE

Beschreibungen/Notizen

• Suicidal enzyme involved in vitamin B1 synthesis Vitamin B1 (thiamin) was the first vitamin to be discovered more than a century ago, but some of the details of its biosynthesis remain unclear because of the complexity and novelty of this process. In yeast, the protein THI4p catalyses the assembly of the thiazole moiety of vitamin B1 in a complex reaction involving the conversion of NAD, glycine and sulphide to an adenylated carboxythiazole phosphate. The source of the sulphide and the mechanism by which it is incorporated into the thiazole is not known. Chatterjee et al . now report the first full reconstitution of THI4p-catalysed thiamin thiazole biosynthesis. They show that a conserved cysteine residue of THI4p acts as the source of sulphur, meaning that this protein is in fact a co-substrate of the biosynthetic pathway. THI4p can do this only once, so that it is a cofactor or 'suicide enzyme' rather that a true multi-turnover enzyme. Thiamine pyrophosphate 1 is an essential cofactor in all living systems 1 . Its biosynthesis involves the separate syntheses of the pyrimidine 2 and thiazole 3 precursors, which are then coupled 2 . Two biosynthetic routes to the thiamine thiazole have been identified. In prokaryotes, five enzymes act on three substrates to produce the thiazole via a complex oxidative condensation reaction, the mechanistic details of which are now well established 2 , 3 , 4 , 5 , 6 . In contrast, only one gene product is involved in thiazole biosynthesis in eukaryotes (THI4p in Saccharomyces cerevisiae ) 7 . Here we report the preparation of fully active recombinant wild-type THI4p, the identification of an iron-dependent sulphide transfer reaction from a conserved cysteine residue of the protein to a reaction intermediate and the demonstration that THI4p is a suicide enzyme undergoing only a single turnover.