Yes, I know that it should be found and hunted (harvested?) first. ;) Let's take assumption that's a carbon based life form using water as solvent. Are the aminoacids that we use the only feasible and convergent evolution would cause that they would have the same? What would be a reaction of human organism for facing mostly the same set but with a few different aminoacids? Would they be also absorbed in digestive track? If they were would our organism be able to decompose them harmlessly? How hard would be chirality to cope with? Could mirror version of known compounds be at least used as source of energy? Should immune system react agressively for such unknown compounds?