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Racemization of alanine by the alanine racemases from Salmonella typhimurium and Bacillus stearothermophilus: energetic reaction profiles

Journal Article · · Biochemistry; (United States)
DOI:https://doi.org/10.1021/bi00409a022· OSTI ID:7143752
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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), Journal Name: Biochemistry; (United States) Vol. 27:9; ISSN BICHA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALANINES
AMINO ACIDS
BACILLUS
BACTERIA
BIOCHEMICAL REACTION KINETICS
CARBOHYDRATES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL WALL
CHALCOGENIDES
DEUTERIUM COMPOUNDS
ENZYMES
GLUCOPROTEINS
HYDROGEN COMPOUNDS
ISOMERASES
ISOTOPE EFFECTS
KINETICS
LABELLED COMPOUNDS
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PROTEINS
RACEMATES
RACEMIZATION
REACTION KINETICS
SACCHARIDES
SALMONELLA
SALMONELLA TYPHIMURIUM
STEREOCHEMISTRY
TRITIUM COMPOUNDS
TRITIUM OXIDES