I'm not inclined to do a bunch of research and I'm not claiming to be the best to interpret the studies, as I don't have a background in biology, but a cursory search shows many results like this https://link.springer.com/article/10.1007/s10545-017-0063-1

I didn't claim I was certain of this however, only that I'm under the impression that amino acid synthesis doesn't work as well for all people, for all amino acids.