Activation of Rat Intestinal Alkaline Phosphatase by Taurine May be an Alternative Mechanism of Endotoxemic Injury Protection

Abstract

Investigation of the effect of taurine on the hydrolysis of para-nitrophenylphosphate (p-NPP) by rat intestinal alkaline phosphatase (ALP), L-phenylalanine inhibition of ALP and the mechanism of ALP activation by taurine as well as its role in endotoxemic injury protection was carried out. Rat intestinal ALP was exposed to taurine, and L-phenylalanine at varying concentrations and periods of time. Substrate concentration-dependent kinetic analysis was carried out at 10 mM concentration of taurine and 5.17mM of p-NPP. The concentration dependent kinetic analysis of L-phenylalanine was also investigated at 60 mM. The partially purified rat intestinal alkaline phosphatase activity was also investigated in the presence of taurine. Their interactive effect on L-phenylalanine inhibition was also analyzed. Investigation of the effect of taurine on rat intestinal ALP hydrolysis of p-NPP revealed that taurine is an activator of intestinal ALP. At 10 mM taurine and 60 mM L-phenylalanine, taurine relieved L-phenylalanine inhibition of rat intestinal ALP. The effect of lipopolysaccharide in the absence and presence of taurine on ALP activity was also carried out in vivo. The kinetic analysis of the data from the in vivo study revealed that rat intestinal ALP activity is higher (12x10^-3nmol ^-1min^-1mg protein) in the presence of taurine and LPS when compared with the activity in the presence of LPS (9x10^-3nmol^-1min^-1mg protein) or taurine (8.8x10^-3nmol^-1min^-1mg protein) alone. From this study, it may be concluded that the activation of rat intestinal ALP by taurine may be one of the mechanisms of endotoxemic injury protection.

Keywords: Intestinal Alkaline Phosphatase, Taurine, Endotoxemic , Lipopolysaccharide