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In vitro oxidation of pyrazinamide and allopurinol by rat liver aldehyde oxidase.
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Aldehyde
oxidase
was
purified
about
120
-
fold
from
rat
liver
cytosol
by
sequential
column
chromatography
using
diethylaminoethyl
(
DEAE
)
cellulose
,
Benzamidine-
Sepharose
6
B
and
gel
filtration
.
The
purified
enzyme
was
shown
as
a
single
band
with
M
(
r
)
of
2
.
7
x
10
(
5
)
on
polyacrylamide
gel
electrophoresis
(
PAGE
)
and
M
(
r
)
of
1
.
35
x
10
(
5
)
on
sodium
dodecyl
sulfate-polyacrylamide
gel
electrophoresis
.
Using
this
purified
enzyme
,
in
vitro
conversion
of
allopurinol
,
pyrazinamide
and
pyrazinoic
acid
was
investigated
.
Allopurinol
and
pyrazinamide
were
oxidized
to
oxypurinol
and
5
-
hydroxy-pyrazinamide
,
respectively
,
while
pyrazinoic
acid
,
the
microsomal
deamidation
product
of
pyrazinamide
,
was
not
oxidized
to
5
-
hydroxypyrazinoic
acid
.
The
apparent
Km
value
of
the
enzyme
for
pyrazinamide
was
160
microM
and
that
for
allopurinol
was
1
.
1
mM
.
On
PAGE
,
allopurinol-
or
pyrazinamide-stained
band
was
coincident
with
Coomassie
Brilliant
Blue
R
250
-
stained
band
,
respectively
.
These
results
suggest
that
aldehyde
oxidase
may
play
a
role
in
the
oxidation
of
allopurinol
to
oxypurinol
and
that
of
pyrazinamide
to
5
-
hydroxypyrazinamide
with
xanthine
dehydrogenase
which
can
oxidize
both
allopurinol
and
pyrazinamide
in
vivo
.
The
aldehyde
oxidase
may
also
play
a
major
role
in
the
oxidation
of
allopurinol
and
pyrazinamide
in
the
subgroup
of
xanthinuria
patients
(
xanthine
oxidase
deficiency
)
who
can
oxidize
both
allopurinol
and
pyrazinamide
.
