The "new" fifth taste, called umami, goes back centuries and was widely used by Japanese cooks.
The taste is created by glutamate, which is a building bloc of proteins and is present almost everywhere in the body.
Glutamate can also function as a neurotransmitter, which does its neurotransmitter thing and doesn't contribute to the umami taste in any way.
Then, there are nucleotides, the building blocks of DNA and RNA. These guys do not create the umami sensation, but they can enhance it for our fun and gustatory pleasure.