well, pretty much any biological molecule is constructed from glucose...
to clear up the confusion:
1) yes, glutamate is the same as MSG. your tongue has receptors for it too, which will potentiate other taste perceptions when stimulated.
2) glutamine is glutamate with an extra amido (not ammonium) group. an important molecule but the neurotransmitter is glutamate.
my all-time favourite is orexin, a neuropeptide that integrates arousal and alertness with motivation and reward. it was discovered only 7 years ago and it's amazing in how many things it has become involved since.
lacking that as an option, I chose dopamine, which is also a good thing to have a lot of.