Mechanistic studies on two enzymes catalyzing substitution reactions on the pyrimidirie moiety of thiamin will be described. Thiamin phosphate synthase catalyzes the displacement of the pyrophosphate of 2-methyl-4-amino5-hydroxymethylpynmidine pyrophosphate by 4 methyl-5-hydroxyethylthiazole phosphate. A mechanism for this reaction which is consistent with substituent effects and with the X ray crystal structure of the enzyme/thiamin phosphate/pyrophosphate ternary complex will be described. Thiaminase I catalyzes the displacement of the thiazole moiety of thiamin by a variety of nucleophiles. A mechanistic proposal for this enzyme will be described. This proposal is consistent with the stereochemistry of the reaction, with the inactivation of the enzyme with 2-methyl-4-amino-6 chloropyrimidine and with the X ray crystal structure of the mechanism based inactivated enzyme.
|Original language||English (US)|
|State||Published - Dec 1 1998|
ASJC Scopus subject areas
- Molecular Biology