589
S-21-2
Pyridoxine
Responsive J.P
Department of Pediatrics, (USA) I.
Unresponsive
KRAUS , and
Homocystinuria
V.KoIcH
University of Colorado School of Medicine, Denver, CO 80262
INTRODUCTION
Cystathionine ƒÀ-Synthase of
and
sulfur
amino
variations
(CBS) acid
and optic
retardation
and
Some
and
This
of
PLP,
attempted
to by
a
correlate
in
in At
the
marked and vivo
the
CBS
gene
BIOCHEMICAL
all, fall
methionine
PLP.
mutations
II.
with
of
not
well
respond
to
to
present
time,
to
structure
the
studies of
are the
with being
in
carried
enzyme
and
its
the
vitamin
and
urinary
studies
vitro
[2]
stimulation
out
to
the
coenzyme.
plasma
biochemical
the
from as
(B6),
elevated
pyridoxine
of in
irreversibly
pyridoxine
previous
have mental
condensation
(PLP)
with
clinical
patients
cysteine
moiety
characteristically
responsiveness
the
5'-phosphate
In
all
Its
including
ultimately
sulfur
treatment
homocyst(e)ine.
Nearly
catalyzes
the
pyridoxal
disorder
man.
manifestations
and
removes
in
[1].
CBS
requires
inherited
homocystinuria
clinical
cystathionine
in their
recessively
of
documented
other
pathway CBS
but
autosomal
cause
disease.
form
cycle.
individuals,
concentrations
activity
to
pathway.
precursor
exhibit
vascular
serine
conservation affected
is an major are
some
thrombotic and
transsulfuration
the
heterogeneity
lenses
homocysteine
methionine
and
biochemical
dislocated
deficiency
metabolism
of
we CBS
correlate
the
responsiveness
to
PLP
.
STUDIES
In order to determine the affinity of normal and mutant CBS apoenzymes for PLP we have developed conditions for growth of human skin fibroblasts in a medium depleted of 136 vitamers. Cellular PLP content fell rapidly when cells were grown in medium containing no pyridoxal (PL) and hydroxylamine-treated human serum. After four passages, the PLP content was lowered to 6% (from 24 to 1 ng PLP/mg cell protein). Depletion of cellular PLP was associated with a sharp fall in the ratio of CBS holoenzyme/total enzyme from 0.7 to
S-21-2
Pyridoxine
Responsive J.P
Department of Pediatrics, (USA) I.
Unresponsive
KRAUS , and
Homocystinuria
V.KoIcH
University of Colorado School of Medicine, Denver, CO 80262
INTRODUCTION
Cystathionine ƒÀ-Synthase of
and
sulfur
amino
variations
(CBS) acid
and optic
retardation
and
Some
and
This
of
PLP,
attempted
to by
a
correlate
in
in At
the
marked and vivo
the
CBS
gene
BIOCHEMICAL
all, fall
methionine
PLP.
mutations
II.
with
of
not
well
respond
to
to
present
time,
to
structure
the
studies of
are the
with being
in
carried
enzyme
and
its
the
vitamin
and
urinary
studies
vitro
[2]
stimulation
out
to
the
coenzyme.
plasma
biochemical
the
from as
(B6),
elevated
pyridoxine
of in
irreversibly
pyridoxine
previous
have mental
condensation
(PLP)
with
clinical
patients
cysteine
moiety
characteristically
responsiveness
the
5'-phosphate
In
all
Its
including
ultimately
sulfur
treatment
homocyst(e)ine.
Nearly
catalyzes
the
pyridoxal
disorder
man.
manifestations
and
removes
in
[1].
CBS
requires
inherited
homocystinuria
clinical
cystathionine
in their
recessively
of
documented
other
pathway CBS
but
autosomal
cause
disease.
form
cycle.
individuals,
concentrations
activity
to
pathway.
precursor
exhibit
vascular
serine
conservation affected
is an major are
some
thrombotic and
transsulfuration
the
heterogeneity
lenses
homocysteine
methionine
and
biochemical
dislocated
deficiency
metabolism
of
we CBS
correlate
the
responsiveness
to
PLP
.
STUDIES
In order to determine the affinity of normal and mutant CBS apoenzymes for PLP we have developed conditions for growth of human skin fibroblasts in a medium depleted of 136 vitamers. Cellular PLP content fell rapidly when cells were grown in medium containing no pyridoxal (PL) and hydroxylamine-treated human serum. After four passages, the PLP content was lowered to 6% (from 24 to 1 ng PLP/mg cell protein). Depletion of cellular PLP was associated with a sharp fall in the ratio of CBS holoenzyme/total enzyme from 0.7 to
