(you said as little research as possible, so I'm intentionally not checking my work.)
ACGT are the codons for DNA tho, not proteins? These four may make up some of the proteins, but I'd guess they're only four of many, and maybe we only use those four for enzyme construction instructions. I know we (animals and fungi) digest other protein from other creatures by denaturing the proteins used in their construction, and we make more DNA from those proteins, but surely there are other proteins that can't be use for making DNA/RNA. Like, we also consume starches and lipids, surely we take those apart and recombine them into new molecules.
I also remember from the "folding @ home" project that it's not enough to know the sequence of proteins, we also need to know their shape in space. Hell, I remember that proteins are asymmetrical, and the property of "chirality" means that a mirror-image of a protein molecule could be biochemically inert to us -- "left-handed" proteins are useless to us if digested. So a linked-list can't be enough.