TITLE:
Characterization of Esterases of Tamarindus indica Seeds
AUTHORS:
S. Kantharaju, K. R. Siddalinga Murthy
KEYWORDS:
Tamarindus indica, Germination, Esterase, α-Naphthylacetate, p-Chloromercuribenzoate, Eserine Sulphate, Dichlorvos
JOURNAL NAME:
Journal of Biosciences and Medicines,
Vol.2 No.4,
June
12,
2014
ABSTRACT: Germinating seeds of Tamarindus indica
synthesizes various enzymes which are required for the degradation of seed
reserves such as xyloglucans, fatty acid esters and proteins. Among these,
esterases, belonging to a group of hydrolytic enzymes catalyze the hydrolysis
of various types of esters. They play an important role in cell expansion as
well as detoxification of xenobiotics and many agrochemicals and insecticides.
The esterases are extracted from the germinating tamarind seeds using 50 mM
phosphate buffer, pH 7. The Km with α-naphthyl acetate as the substrate is
19.23 μM and the enzymes are optimally active at pH 7.0 to 7.5 and are stable
between pH 5.0 to 9.0. The optimum temperature of esterase activity of tamarind
seed is between 37?C - 50?C and is stable up to 40?C. The activity declined by
30% at 60?C and about 90% at 70?C. Highest esterase activity and specific
activity are observed on the 21st day of germination. The polyacrylamide gel
electrophoresis (PAGE) indicated the presence of nine isozymes of esterases.
Band numbers 1, 5 and 6 are the major esterolytic bands present throughout the
germination period while band numbers 2 & 3 are minor bands present only
during the latter period of the germination. Based on substrate and inhibitor
specificity in conjunction with electrophoresis, the esterases 1 to 8 have been
classified as carboxylesterases sensitive to organophosphate inhibitor (OP) and
PCMB (p-chloromercuribenzoate) while esterase 9 is classified as carboxylesterase
sensitive to OP. These esterases are unaffected by carbamate inhibitor, eserine
sulphate.