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PMID:1358877
| Citation |
Choi, SY, Esaki, N, Yoshimura, T and Soda, K (1992) Reaction mechanism of glutamate racemase, a pyridoxal phosphate-independent amino acid racemase. J. Biochem. 112:139-42 |
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| Abstract |
Glutamate racemase of Pediococcus pentosaceus contained no cofactor, and was completely inactivated by a thiol reagent. The role of a cysteine residue in the enzyme reaction was studied by chemical modification. The modification of this cysteine residue resulted in a concomitant loss of activity. DL-Glutamate protected the enzyme from inactivation. The inactivated enzyme was reactivated by addition of dithiothreitol. The racemization in 2H2O showed an overshoot in the optical rotation of glutamate before the substrate was completely racemized. This indicates that the removal of alpha-hydrogen is the rate determining step. During the racemization of D- or L-glutamate in 3H2O, tritium was incorporated preferentially into the product. Glutamate is racemized by the enzyme probably through a two base mechanism. |
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| Keywords |
Amino Acid Isomerases/chemistry; Amino Acid Isomerases/drug effects; Bacterial Proteins/chemistry; Bacterial Proteins/drug effects; Cysteine/chemistry; Deuterium; Enzyme Activation; Glutamates/chemistry; Glutamates/pharmacology; Glutamic Acid; Kinetics; Magnetic Resonance Spectroscopy; Pediococcus/enzymology; Pyridoxal Phosphate/chemistry; Sulfhydryl Compounds; Tritium |
| edit table |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0016853: isomerase activity |
ECO:0000269: |
F |
Figure 1 indicates a decrease in optical rotation as a results of a structural change observed in the alpha position of the L-glutamate substrate. This results are observed during the incubation with glutamate racemase in deuterium oxide. |
complete | ||||
| GO:0016855: racemase and epimerase activity, acting on amino acids and derivatives |
ECO:0000314: |
F |
Figure 3 and 4 indicate that the reaction is reversible, and modification of 1 mol of cysteine per mol of enzyme resulted in complete loss of activity. This shows that one of two bases involved in catalysis of the enzyme is the cysteine residue. |
complete | ||||
See also
References
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