| Summary: | Esterases are ubiquitous in living organisms and perform multiple functions in animals, plants,
insects and microorganisms. Insect esterases broadly perform physiological and defense functions.
The present work aims towards identifying heat stable esterase in the hemolymph of near isogenic
lines (NILs) and their parents, and further to classify esterases based on substrate-inhibition reactions
in silkworm, Bombyx mori. Five different α-esterases viz. Est-1, Est-2, Est-3, Est-4 and Est-5 were
observed in this study. Of them, Est-1 and Est-2 were monomorphic and, Est-3, Est-4 and Est-5 were
polymorphic. Heat stability studies revealed Est-2 and Est-3 as heat stable and, Est-1, Est-4 and Est-5
as heat liable. Through inhibition analysis, Est-1 was identified as cholinesterase and Est-5 as
carboxylesterase because their activity was totally inhibited, respectively, by eserine sulphate and
phenylmethylsulfonyl fluoride (PMSF) while Est-3 was inhibited by both the inhibitors. The Est-2 and
Est-4 were unaffected by both PMSF and eserine sulphate. The isozyme patterns of breed specific as
well as heat stable esterases supports the variations in the survival percentage of silkworm breeds at
high temperatures. This study enhances the knowledge on esterase-mediated thermotolerance in B.
mori.
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