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FMO3

FMO3, or flavin-containing monooxygenase 3, is an enzyme in the flavin-containing monooxygenase family that catalyzes the oxygenation of a range of xenobiotics and endogenous compounds. In humans, FMO3 is the principal hepatic FMO responsible for the N-oxidation of many substrates, most notably the conversion of trimethylamine to trimethylamine N-oxide (TMAO).

Biochemical properties: It resides mainly in the endoplasmic reticulum of hepatocytes and uses flavin adenine dinucleotide

Genetics and clinical significance: The FMO3 gene is located on chromosome 1q24.3 and encodes the protein. Common

Expression and substrate range: FMO3 is most abundant in liver but is also detectable in kidney, intestine,

(FAD)
as
a
prosthetic
group
and
NADPH
as
an
electron
donor.
The
reaction
introduces
one
atom
of
oxygen
into
the
substrate
(monooxygenation)
with
the
concurrent
reduction
of
O2
to
water,
producing
the
N-oxide
product
for
amines
such
as
TMA.
allelic
variants
influence
the
rate
of
metabolism
of
FMO3
substrates.
Loss-of-function
mutations
can
result
in
trimethylaminuria
(fish
odor
syndrome),
a
condition
characterized
by
accumulation
and
excretion
of
TMA
due
to
impaired
oxidation
to
TMAO.
The
condition
is
usually
inherited
in
an
autosomal
recessive
manner.
and
other
tissues.
Beyond
TMA,
the
enzyme
metabolizes
a
variety
of
tertiary
amines,
thioethers,
sulfoxides,
and
sulfides,
contributing
to
the
metabolism
of
certain
pharmaceuticals
and
other
xenobiotics.