I am interested in whether any examples are known of enzymes whose
expression is induced by high levels of their reaction product, rather
than of their substrates. (I exclude enzymes involved in cycles, where
the distinction betweeen substrate and product may be unclear.) It
seems to me that this is a reasonable concept in principle -- if the
product is abundant then the enzyme that is already in existence must
be working hard, so maybe it is limiting and making more of it would be
beneficial. Presumably this would generally be inferior to induction
based on substrate levels, but scenarios can be imagined in which the
substrate is very unsuited to participating in signal transduction: an
example might be superoxide dismutase, whose product (H2O2) can diffuse
across cellular distances but whose substrate cannot.
Are examples known, or suspected?
Aubrey de Grey
