Purification and characterization of insulin-mimetic inositol phosphoglycan-like molecules from grass pea (Lathyrus sativus) seeds

Background: Signal transduction through the hydrolysis of glycosyl-phosphat idylinositol (GPI) leading to the release of the water-soluble inositol pho sphoglycan (IPG) molecules has been demonstrated to be important for mediat ing some of the actions of insulin and insulin-like growth factor-I (IGF-I) . Materials and Methods: in the present study, GPI from grass pea (Lathyrus s ativus) seeds has been purified and partially characterized on the basis of its chromatographic properties and its compositional analysis. Results: The results indicate that it shows similarities to GPI previously isolated from other sources such as rat liver. IPG was generated from L. sa tivus seed GPI by hydrolysis with a GPI-specific phospholipase D (GPI-PLD). This IPG inhibited protein kinase A (PKA) in an in vitro assay, caused cel l proliferation in explanted cochleovestibular ganglia (CVG), and decreased 8-Br-cAMP-induced phosphoenolpyruvate carboxykinase (PEPCK) mRNA expressio n in cultured hepatoma cells. Conclusions: Our data indicate that L. sativus seed IPG possess insulin-mim etic activities. This may explain why L. sativus seeds have been used in so me traditional medicines to ameliorate diabetic symptoms.