Enzyme
With
Repressor
Function -
Although
most
of
the
repressor
proteins
(lac,
gal,
tryp)
known
today
do
not
possess
any
enzymatic
activity,
recently
an
enzyme
has
been
found
to
have
repressor
functions.
In
S.typhimurium
the
synthesis
of
four
enzymes
involved
in
the
degradation
of
histidine
to
glutamate
and
formate
is
under
the
control
of
two
Hut
operons.
The
enzyme
glutamine
synthetase,
which
is
nonadenylated
and
present
in
large
amounts
when
grown
in
nitrogen
limited
media
is
found
to
bind
to
the
hut
operon
and
promote
transcription.
Although
this
is
one
example
available
at
present,
it
is
likely
that
there
may
be
other
instances
where
regulation
occurs
through
the
binding
activity
of
proteins
which
also
have
catalytic
activity.
