Umami is indeed associated with glutamate, in all its natural and contrived forms: MSG, Marmite & Vegemite, seaweed, slow-cooked or grilled meat, mushrooms, aged cheeses, anchovies, fermented soybeans, etc.

I remember reading somewhere, recently, that the concept of this "fifth taste" has been promoted heavily for decades by a Japanese "scientist" employed by the Ajinomoto commpany, producer of 1/3 of the world's MSG (also the biggest producer of the artificial sweetener aspartame). I can't recall the source but I'll try to look it back up.

Umami, as a concept and ready-made flavouring, has gradually achieved wider acceptance thanks to the company's shameless self-promotion, but those who tend to react to MSG should proceed towards with extreme caution, if at all!