Characterization of Esterases of Tamarindus Indica Seeds

Germinating seeds of Tamarindus indicasynthesizes various enzymes which are required for the degradation of seedreserves such as xyloglucans, fatty acid esters and proteins. Among these,esterases, belonging to a group of hydrolytic enzymes catalyze the hydrolysisof various types of esters. They play an important role in cell expansion aswell as detoxification of xenobiotics and many agrochemicals and insecticides.The esterases are extracted from the germinating tamarind seeds using 50 mMphosphate buffer, pH 7. The Km with α-naphthyl acetate as the substrate is19.23 μM and the enzymes are optimally active at pH 7.0 to 7.5 and are stablebetween pH 5.0 to 9.0. The optimum temperature of esterase activity of tamarindseed is between 37C - 50C and is stable up to 40C. The activity declined by30% at 60C and about 90% at 70C. Highest esterase activity and specificactivity are observed on the 21st day of germination. The polyacrylamide gelelectrophoresis (PAGE) indicated the presence of nine isozymes of esterases.Band numbers 1, 5 and 6 are the major esterolytic bands present throughout thegermination period while band numbers 2 & 3 are minor bands present onlyduring the latter period of the germination. Based on substrate and inhibitorspecificity in conjunction with electrophoresis, the esterases 1 to 8 have beenclassified as carboxylesterases sensitive to organophosphate inhibitor (OP) andPCMB (p-chloromercuribenzoate) while esterase 9 is classified as carboxylesterasesensitive to OP. These esterases are unaffected by carbamate inhibitor, eserinesulphate