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Cross‐linking of serine racemase dimer by reactive oxygen species and reactive nitrogen species
Author(s) -
Wang Wei,
Barger Steven W.
Publication year - 2012
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.22832
Subject(s) - peroxynitrite , chemistry , dimer , reactive oxygen species , serine , superoxide , nmda receptor , nitric oxide , reactive nitrogen species , biochemistry , receptor , enzyme , organic chemistry
Serine racemase (SR) is the only identified enzyme in mammals responsible for isomerization of L‐serine to D‐serine, a coagonist at N‐methyl‐D‐aspartate (NMDA) receptors in the forebrain. Our previous data showed that an apparent SR dimer resistant to sodium dodecyl sulfate and β‐mercaptoethanol was elevated in microglial cells after proinflammatory activation. Because the activation of microglia is typically associated with an oxidative burst, oxidative cross‐linking between SR subunits was speculated. In this study, an siRNA technique was employed to confirm the identity of this SR dimer band. The oxidative species potentially responsible for the cross‐linking was investigated with recombinant SR protein. The data indicate that nitric oxide, peroxynitrite, and hydroxyl radical were the likely candidates, whereas superoxide and hydrogen peroxide per se failed to contribute. Furthermore, the mechanism of formation of SR dimer by peroxynitrite oxidation was studied by mass spectrometry. A disulfide bond between Cys 6 and Cys 113 was identified in 3‐morpholinosydnonimine hydrochloride (SIN‐1)‐treated SR monomer and dimer. Activity assays indicated that SIN‐1 treatment decreased SR activity, confirming our previous conclusion that noncovalent dimer is the most active form of SR. These findings suggest a compensatory feedback in which the consequences of neuroinflammation might dampen D‐serine production to limit excitotoxic stimulation of NMDA receptors. © 2012 Wiley Priodicals, Inc.