Taurine is a derivative of the amino acid cysteine, formed by its decarboxylation and oxidation of the sulfhydryl group to the sulfone group. In the organism, it is important for the second phase biotransformation reactions. Conjugation of some substances with taurine increases their solubility in water and thus facilitates their excretion. Some bile acids (e.g. taurocholic acid) are also conjugated with taurine. The sulfone group is relatively strongly acidic, so it is ionized in virtually all environments common in the body, which is important for the emulsifying function of these bile acids.