Ja. Argentine et Aa. James, CHARACTERIZATION OF A SALIVARY GLAND-SPECIFIC ESTERASE IN THE VECTOR MOSQUITO, AEDES-AEGYPTI, Insect biochemistry and molecular biology, 25(5), 1995, pp. 621-630
Esterase enzymatic activity was investigated in salivary gland lysates
of adult Aedes aegypti. Esterases in lysates made from female glands
had higher specific activity than those in lysates from male glands to
wards beta-naphthyl acetate but showed no difference with alpha-naphth
yl butyrate as a substrate. Female salivary gland lysates showed no di
fference in activity to alpha- and beta-forms of naphthyl acetate and
no discernable activity towards alpha-naphthyl caprate. Both female an
d male salivary gland lysates exhibited phosphatase enzymatic activity
but the specific activities were lower than those seen for the estera
se enzymatic activity. Salivary gland esterase activity was inhibited
completely by paraoxon, para-hydroxymercurobenzoate, tetraethylammoniu
m iodide and moderately by diisopropylfluorophosphate. Eserine and phe
nylmethylsulfonylfluoride had no effect on enzyme activity. In a probi
ng assay, adults of both sexes were shown to secrete esterase in saliv
a, Esterase activity was present in the saliva of females probing for
either a sugar meal or a blood meal. Furthermore, esterase was secrete
d from female salivary glands in culture. Histochemical analysis. of d
issected salivary glands showed that the majority of the esterase enzy
matic activity was in the distal-lateral lobes of the female tissues,
although the proximal-lateral and medial lobes also had activity. Male
salivary glands stained uniformly over all of the lobes. A salivary g
land-specific esterase, designated SG-EST, appears to account for the
majority of enzyme activity in the glands. SG-EST was partially purifi
ed by electroelution of an active protein from native polyacrylamide g
els, and has an approximate molecular weight of 65,000 Da. In separate
experiments, affinity chromatography independently-identified a singl
e 65,000 Da protein likely to be SG-EST. Native electrophoretic analys
is of salivary glands revealed that, while most enzyme activity is due
to SG-EST, there are two other esterases present. One of these minor
moieties is present in adult tissues in addition to the salivary gland
, and the other is present throughout development, Possible functions
of the salivary gland esterase are discussed.