| dc.description.abstract | Body louse Pediculus humanus humanus, belong to the group of blood-sucking
insects that act as vectors of several deadly diseases to either Mankind or his
Livestock, resulting in massive economic losses, especially in third world countries
where these diseases are prevalent. Body louse are host specific and feed exclusively
on blood. Because of their feeding habits they are therefore prone to blood-borne
control agents. Proteins are by far the most abundant nutrients of a bloodmeal. Hence
the characterization of enzymes involved in bloodmeal digestion is crucial in
understanding their physiological role within the body louse. In this study,
Aminopeptidase was characterized from Midgut of human body louse Pediculus
humanus humanus which had been dissected 24 hrs after bloodmeal. In crude midgut
homogenate, the aminopeptidase showed optimum activity at pH 8.0 (Alkaline) using
Leucine para nitoanilide as the sub,strate. Body louse midgut aminopeptidase is fairly
thermally stable, incubation at 50°C for 150 min resulted in 80% remaining activity.
Supernatants from midgut homogenized in 1% Tween 20 showed 2.5 fold
increase in enzyme activity; while midguts homogenized in 1% Triton X-IOO showed
8.0 fold increase in enzyme activity. Aminopeptidase inthe midgut of body louse is
stimulated by bloodmeal and increases gradually with time after feeding. Maximal
release is realized 48 hrs after bloodmeal. The activity persisted even 96 hrs after
bloodrneal. The pattern of feeding in both female adults and newly hatched nymphs
remained fairly similar.
Kinetic studies showed that the enzyme exists in two forms of soluble and
membrane bound. However it exhibited different catalytic activity with regard to Vmax
but had the same Km value. The enzyme activity was inhibited by and l' 1a
Phenanthroline and Mn2+. The enzyme activity in homogenate supernatant was
restricted to one peak after partial purification using Gel Filtration Chromatography on
Superose 6. Only one peak of 67 KDa - 69 KDa was observed after separation of
homogenates extracted with or without Triton Xvl Ou. Fractions purified from
Superose 6 revealed one band of 69 KDa on Native PAGE with homogenates
extracted in saline buffer and two bands of 67 KDa and 69 KDa with homogenates
extracted in 1% Triton X-lOa. In-gel staining of the enzyme activity revealed one band
of Mr=70,OOO. These results indicate that Aminopeptidase is one of the major digestive
enzyme in the body louse | en |
