Tuftsin diacetate, a tetrapeptide, is a macrophage/microglial activator. Tuftsin is a tetrapeptide, Thr-Lys-Pro-Arg, which resides in the Fc-domain of the heavy chain of immunoglobulin G. Tuftsin possesses a broad spectrum of activities related primarily to the immune system function and exerts on phagocytic cells, notably on macrophages.

4-Acetamidobutanoic acid can be found in blood feces and urine as well as in human prostate tissue. 4-Acetamidobutanoic acid exists in all eukaryotes ranging from yeast to humans.

3-oxoglutaric acid or acetonedicarboxylic acid is a simple carboxylic acid which may be used as a building block in organic chemistry. It has been found to be a microbial metabolite.