Reactivity of taurine with aldehydes and its physiological role

Chemical reactions of the amino group of taurine with aldehyde were investigated. Glucose, acetaldehyde, and malondialdehyde (MDA) were used as aldehydes. After taurine was reacted with the aldehydes, the amounts of remaining taurine and aldehydes were measured, and thereby the reactivity was evaluated. The amino acids such as glycine, alpha-alanine, and beta-alanine were compared because of their structural resemblance to each other. Taurine showed a high reactivity with each one of the aldehydes tested. It is known that protein is altered through reactions of the amino group with various aldehydes. Low density lipoprotein (LDL) was used as a model protein, and the inhibiting effect of taurine against the modification of LDL by MDA was examined. Our results indicate that taurine inhibited the production of LDL modified by MDA. It was shown that the inhibiting effects correlated with the reactivity of MDA with the amino acids. Further, the taurine-glucose reaction product showed an antioxidative effect on the peroxidation of liposomes made of yolk phosphatidylcholine as a biomembrane model. The results suggest the possibility of an inhibiting effect of taurine against the modification of protein, as well as an antioxidative effect through the reactions of taurine with aldehydes in vivo.