Abstract
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) |
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Journal | FASEB Journal |
Volume | 12 |
Issue number | 8 |
State | Published - Dec 1 1998 |
ASJC Scopus subject areas
- Biotechnology
- Biochemistry
- Molecular Biology
- Genetics