Abstract
Mammalian brain contains high levels of D-serine, an endogenous co-agonist of N-methyl D-aspartate type of glutamate receptors. D-Serine is synthesized by serine racemase, a brain enriched enzyme converting L- to D-serine. Degradation of D-serine is achieved by D-amino acid oxidase, but this enzyme is not present in forebrain areas that are highly enriched in D-serine. We now report that serine racemase catalyzes the degradation of cellular D-serine itself, through the α,β-elimination of water. The enzyme also catalyzes water α,β-elimination with L-serine and L-threonine. α,β- Elimination with these substrates is observed both in vitro and in vivo. To investigate further the role of α,β-elimination in regulating cellular D-serine, we generated a serine racemase mutant displaying selective impairment of α,β-elimination activity (Q155D). Levels of D-serine synthesized by the Q155D mutant are several-fold higher than the wild-type both in vitro and in vivo. This suggests that the α,β-elimination reaction limits the achievable D-serine concentration in vivo. Additional mutants in vicinal residues (H152S, P153S, and N154F) similarly altered the partition between the α,β-elimination and racemization reactions. α,β-Elimination also competes with the reverse serine racemase reaction in vivo. Although the formation of L- from D-serine is readily detected in Q155D mutant-expressing cells incubated with physiological D-serine concentrations, reversal with wild-type serine racemase-expressing cells required much higher D-serine concentration. We propose that α,β-elimination provides a novel mechanism for regulating intracellular D-serine levels, especially in brain areas that do not possess D-amino acid oxidase activity. Extracellular D-serine is more stable toward α,β-elimination, likely due to physical separation from serine racemase and its elimination activity.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1754-1763 |
| Number of pages | 10 |
| Journal | Journal of Biological Chemistry |
| Volume | 280 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jan 21 2005 |
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ASJC Scopus subject areas
- Biochemistry
Cite this
Serine racemase modulates intracellular D-serine levels through an α,β-elimination activity. / Foltyn, Veronika N.; Bendikov, Inna; De Miranda, Joari; Panizzutti, Rogerio; Dumin, Elena; Shleper, Maria; Li, Pu; Toney, Michael D.; Kartvelishvily, Elena; Wolosker, Herman.
In: Journal of Biological Chemistry, Vol. 280, No. 3, 21.01.2005, p. 1754-1763.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Serine racemase modulates intracellular D-serine levels through an α,β-elimination activity
AU - Foltyn, Veronika N.
AU - Bendikov, Inna
AU - De Miranda, Joari
AU - Panizzutti, Rogerio
AU - Dumin, Elena
AU - Shleper, Maria
AU - Li, Pu
AU - Toney, Michael D.
AU - Kartvelishvily, Elena
AU - Wolosker, Herman
PY - 2005/1/21
Y1 - 2005/1/21
N2 - Mammalian brain contains high levels of D-serine, an endogenous co-agonist of N-methyl D-aspartate type of glutamate receptors. D-Serine is synthesized by serine racemase, a brain enriched enzyme converting L- to D-serine. Degradation of D-serine is achieved by D-amino acid oxidase, but this enzyme is not present in forebrain areas that are highly enriched in D-serine. We now report that serine racemase catalyzes the degradation of cellular D-serine itself, through the α,β-elimination of water. The enzyme also catalyzes water α,β-elimination with L-serine and L-threonine. α,β- Elimination with these substrates is observed both in vitro and in vivo. To investigate further the role of α,β-elimination in regulating cellular D-serine, we generated a serine racemase mutant displaying selective impairment of α,β-elimination activity (Q155D). Levels of D-serine synthesized by the Q155D mutant are several-fold higher than the wild-type both in vitro and in vivo. This suggests that the α,β-elimination reaction limits the achievable D-serine concentration in vivo. Additional mutants in vicinal residues (H152S, P153S, and N154F) similarly altered the partition between the α,β-elimination and racemization reactions. α,β-Elimination also competes with the reverse serine racemase reaction in vivo. Although the formation of L- from D-serine is readily detected in Q155D mutant-expressing cells incubated with physiological D-serine concentrations, reversal with wild-type serine racemase-expressing cells required much higher D-serine concentration. We propose that α,β-elimination provides a novel mechanism for regulating intracellular D-serine levels, especially in brain areas that do not possess D-amino acid oxidase activity. Extracellular D-serine is more stable toward α,β-elimination, likely due to physical separation from serine racemase and its elimination activity.
AB - Mammalian brain contains high levels of D-serine, an endogenous co-agonist of N-methyl D-aspartate type of glutamate receptors. D-Serine is synthesized by serine racemase, a brain enriched enzyme converting L- to D-serine. Degradation of D-serine is achieved by D-amino acid oxidase, but this enzyme is not present in forebrain areas that are highly enriched in D-serine. We now report that serine racemase catalyzes the degradation of cellular D-serine itself, through the α,β-elimination of water. The enzyme also catalyzes water α,β-elimination with L-serine and L-threonine. α,β- Elimination with these substrates is observed both in vitro and in vivo. To investigate further the role of α,β-elimination in regulating cellular D-serine, we generated a serine racemase mutant displaying selective impairment of α,β-elimination activity (Q155D). Levels of D-serine synthesized by the Q155D mutant are several-fold higher than the wild-type both in vitro and in vivo. This suggests that the α,β-elimination reaction limits the achievable D-serine concentration in vivo. Additional mutants in vicinal residues (H152S, P153S, and N154F) similarly altered the partition between the α,β-elimination and racemization reactions. α,β-Elimination also competes with the reverse serine racemase reaction in vivo. Although the formation of L- from D-serine is readily detected in Q155D mutant-expressing cells incubated with physiological D-serine concentrations, reversal with wild-type serine racemase-expressing cells required much higher D-serine concentration. We propose that α,β-elimination provides a novel mechanism for regulating intracellular D-serine levels, especially in brain areas that do not possess D-amino acid oxidase activity. Extracellular D-serine is more stable toward α,β-elimination, likely due to physical separation from serine racemase and its elimination activity.
UR - http://www.scopus.com/inward/record.url?scp=19944432442&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=19944432442&partnerID=8YFLogxK
U2 - 10.1074/jbc.M405726200
DO - 10.1074/jbc.M405726200
M3 - Article
C2 - 15536068
AN - SCOPUS:19944432442
VL - 280
SP - 1754
EP - 1763
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 3
ER -