1. A comparative Study of Serine
racemase in normal and
schizophrenic patients
Dr Fatima Shad Kaneez
Professor
Panjwani Center For Molecular Medicine and Drug Research
International Center For Chemical and Biological Sciences
University of Karachi. Pakistan
2. 1. Schizophrenia is a brain disease that has afflicted
human since the beginning of written history.
2. Several lines of evidence focus on a direct
involvement of the glutamergic system in the
pathophysiology of psychosis.
3. The hypo function of the ionotropic glutamate N-
methyl-D-Aspartate Receptor (NMDAR) has been
proposed as a model of schizophrenia in humans.
4. D-serine, an endogenous co agonist to the NMDA
subtype glutamate receptor, may be implicated in
schizophrenia (SCZ)
5. Differences between the plasma serine racemase
levels of normal and schizophrenic patients and
estimated the D-isomers excreted in their urine
indicating the importance of serine racemase in
Schizophrenia.
3. Present study aims to:
(1) Identify biological factors responsible for
alterations in D-serine synthesis
(2) Measure differences between the plasma
serine racemase levels of normal and
schizophrenic patients
(3) Estimate the D-isomers excreted in their
urine.
(4) Factors affecting regulation of serine
racemase activities
4. The "Serine racemase" levels in the plasma of
normal and mental health patients were analyzed by
gas chromatography (GC) and GC-mass spectrometry
techniques.
The components in the samples were identified by
comparison of their mass spectra to reference data
bases in conjunction with their retention indices, and
they were quantified as appropriate.
Later on the regulation of serine racemase activity
by amino acids such as glycine and l-aspartic acid
were measured as literature indicated that
alterations in the concentrations of these amino
acids might play a role in the regulation of d-serine
synthesis.
5. Urine samples of both normal and schizophrenic
patients were analyzed by GCMS (Gas
Chromatography Mass Selectivity) detector.
We are proposing that racemization of serine (which
is catalyzed by serine racemase, a pyridoxal 5'-
phosphate-dependent enzyme expressed mainly in
brain and liver) is associated with Schizophrenia.
6. Racemization of serine is catalyzed by serine
racemase, a pyridoxal 5'-phosphate-dependent
enzyme expressed mainly in brain and liver. NMDA
receptor over activation has been implicated in a
number of pathological conditions and inhibitors
of serine racemase are thus potentially
interesting targets for therapy
8. SUBJECTS & METHODS
Blood collection: Forty drug naïve patients
with a DSM- 1VR Diagnosis of
Schizophrenia (American Psychiatric
Association 2000) and attending the
Psychiatric Department at the Al Ain
Hospital, Al Ain (UAE), were recruited for
the study.
Approval was obtained from the Ethics
Review Board and Informed consent was
obtained from the patients prior to
collection of blood and urine samples.
Whole blood (20 ml) was collected from
fasted (12 hours) patients. Special
attention were applied to ensure the
optimization of the serum state for
measuring serine racemase.
9. METHODS
Organic analysis:
The "Serine racemase" levels in the
plasma of normal and mental health
patients were analyzed by gas
chromatography (GC) and GC-mass
spectrometry techniques.
The components in the samples were
identified by comparison of their mass
spectra to reference data bases in
conjunction with their retention indices,
and were quantified as appropriate.
10. Blood sample were stored at -70°C for further use.
Isolation soluble serum fraction of serine
racemase, plasma was re suspended in *lyses buffer
Lysed by three 20 s bursts of sonication.
After centrifugation (15000×g, 30 min, 4°C), the
resulting supernatant will be purified by ion
exchange chromatography using Q-Sepharose Fast
Flow (pH 7.2, lyses buffer, elution by NaCl gradient)
and gel filtration chromatography (lysis buffer+150
mM NaCl).
*(50 mM 2-[4-(2-hydroxyethyl)-1-piperazinyl]-ethanesulfonic acid (HEPES) pH 7.2, 10% (v/v) glycerol, 1 mM MgCl2, 0.1 mM
dithiothreitol (DTT), 1 mM phenylmethylsulfonyl fluoride, 0.05% (w/v) polyethyleneglycol 8000, 50 mM NaCl and 50 M pyridoxal 5'-
phosphate (PLP))
11. Total run time was shortened from 45 to 25 minutes
without any significant loss of resolution.
14. CLINICAL RELEVANCE
There is increasing evidence from
pharmacological (Hashimoto et al 2003) and
genetic (De Miranda et al 2000) studies that
suggest that D-serine, an endogenous coagonist to
the NMDA subtype glutamate receptor, may be
implicated in schizophrenia (SCZ) (Yamada et al
2005).
Although an association of genes for D-serine
degradation, such as D-amino acid oxidase and
G72, has been reported, a role for D-serine in SCZ
has been unclear.
15. We believe that the findings from this study,
along with other preclinical and clinical data on
dopamine-glutamate interaction will have
implications for new pharmacological strategies
for the treatment of psychosis in general and
SCZ in particular.
