Racemization of alanine by the alanine racemases from Salmonella typhimurium and Bacillus stearothermophilus: energetic reaction profiles
Alanine racemases are bacterial pyridoxal 5'-phosphate (PLP) dependent enzymes providing D-alanine as an essential building block for biosynthesis of the peptidoglycan layer of the cell wall. Two isozymic alanine racemases, encoded by the dadB gene and the alr gene, from the Gram-negative mesophilic Salmonella typhimurium and one from the Gram-positive thermophilic Bacillus stearothermophilus have been examined for the racemization mechanism. Substrate deuterium isotope effects and solvent deuterium isotope effects have been measured in both L ..-->.. D and D..-->.. L directions for all three enzymes to assess the degree to which abstraction of the ..cap alpha..-proton or protonation of substrate PLP carbanion is limiting in catalysis. Additionally, experiments measuring internal return of ..cap alpha..-/sup 3/H from substrate to product and solvent exchange/substrate conversion experiments in /sup 3/H/sub 2/O have been used with each enzyme to examine the partitioning of substrate PLP carbanion intermediates and to obtain the relative heights of kinetically significant energy barriers in alanine racemase catalysis.
- Research Organization:
- Massachusetts Institute of Technology, Cambridge (USA)
- OSTI ID:
- 7143752
- Journal Information:
- Biochemistry; (United States), Vol. 27:9
- Country of Publication:
- United States
- Language:
- English
Similar Records
Enzymatic characterization and crystal structure of biosynthetic alanine racemase from Pseudomonas aeruginosa PAO1
Structural and functional adaptation of vancomycin resistance VanT serine racemases
Related Subjects
ALANINES
ISOTOPE EFFECTS
RACEMIZATION
ISOMERASES
BIOCHEMICAL REACTION KINETICS
BACILLUS
CELL WALL
DEUTERIUM COMPOUNDS
GLUCOPROTEINS
RACEMATES
SALMONELLA TYPHIMURIUM
STEREOCHEMISTRY
TRITIUM OXIDES
AMINO ACIDS
BACTERIA
CARBOHYDRATES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHALCOGENIDES
ENZYMES
HYDROGEN COMPOUNDS
KINETICS
LABELLED COMPOUNDS
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PROTEINS
REACTION KINETICS
SACCHARIDES
SALMONELLA
TRITIUM COMPOUNDS
550201* - Biochemistry- Tracer Techniques