I doubt that this is how wordy your communication is.
“It consists of a few systems” would be adequate. And if we had prior context about what else exists that surrounds “the substrate” the “substrate itself” distinction would be meaningful, but it’s not, because you are referring to one object, which is the system you built, and I doubt any enzymes act on it, so it’s likely not a substrate.
“The substrate itself consists of a few systems…”
I doubt that this is how wordy your communication is.
“It consists of a few systems” would be adequate. And if we had prior context about what else exists that surrounds “the substrate” the “substrate itself” distinction would be meaningful, but it’s not, because you are referring to one object, which is the system you built, and I doubt any enzymes act on it, so it’s likely not a substrate.