Blood Digestion in the Mosquito, Anopheles stephensi Liston (Diptera: Culicidae): Activity and Distribution of Trypsin, Aminopeptidase, and α-Glucosidase in the Midgut

Abstract

The activities of trypsin, aminopeptidase, and alpha-glucosidase were studied in the whole midgut, anterior and posterior midgut, and posterior midgut lumen and epithelium of the mosquito Anopheles stephensi Liston. Trypsin activity was restricted entirely to the posterior midgut lumen. No trypsin activity was found before the blood meal, but activity increased continuously up to 30 h after feeding, and subsequently returned to baseline levels by 60 h. Aminopeptidase was active in anterior and posterior midgut regions before and after feeding. In whole midguts, activity rose from a baseline of approximately 3 enzyme units (EU) per midgut to a maximum of 12 EU at 30 h after the blood meal, subsequently falling to baseline levels by 60 h. A similar cycle of activity was observed in the posterior midgut and posterior midgut lumen, whereas aminopeptidase in the posterior midgut epithelium decreased in activity during digestion. Aminopeptidase in the anterior midgut was maintained at a constant low level, showing no significant variation with time after feeding. alpha-glucosidase was active in anterior and posterior midguts before and at all times after feeding. In whole midgut homogenates, alpha-glucosidase activity increased slowly up to 18 h after the blood meal, then rose rapidly to a maximum at 30 h after the blood meal, whereas the subsequent decline in activity was less predictable. All posterior midgut activity was restricted to the posterior midgut lumen. Depending upon the time after feeding, greater than 25% of the total midgut activity of alpha-glucosidase was located in the anterior midgut. The enzyme distributions are consistent with described structural models for digestion in mosquitoes. After blood meal ingestion, proteases are active only in the posterior midgut. Trypsin is the major primary hydrolytic protease and is secreted into the posterior midgut lumen without activation in the posterior midgut epithelium. Aminopeptidase activity is also luminal in the posterior midgut, but cellular aminopeptidases are required for peptide processing in both anterior and posterior midguts. alpha-glucosidase activity is elevated in the posterior midgut after feeding in response to the blood meal, whereas activity in the anterior midgut is consistent with a nectar-processing role for this midgut region.

Interaction between Host Complement and Mosquito-Midgut-StagePlasmodium berghei

“…The other component of the convertase is Bb, which is generated when factor B binds to C3b (or C3i), and is cleaved by factor D. This releases a small fragment, Ba, and generates the enzymatically active complex C3bBb (or C3iBb). Amplification of this process occurs on foreign (activating) surfaces where C3b is protected from degradation by factors I and H. Binding of additional C3b to the C3bBb complex produces the C5 convertase, (C3b) 2 Bb, which cleaves C5 into C5a and C5b, which initiates formation of the MAC. C5b binds to C6 and C7, producing a complex which can associate with cell membranes; subsequent binding of C8 and C9 forms a pore in the membrane that results in lysis of the attacked cell (reviewed in reference 30).…”

The Agrarian Economy of Oman (132-280/749-893) in Arabic Sources

“…In this study, mosquitoes that were previously fed two blood meals exhibited a tendency to having a higher oocyst infection rate than mosquitoes feeding on a single blood meal or none at all. Blood feeding increases enzyme secretions, which can be deleterious to midgut parasites (Gass 1977), however such enzyme activity peaks at 36 hrs (Billingsley and Hecker 1991, Chadee and Beier 1995). In our study, blood meals were offered after a two day interval, a time period that is sufficient for the normalization of enzyme activity.…”

Proteolytic enzymes of female Anopheles: Biphasic synthesis, regulation, and multiple feeding

“…Altogether, the occurrence of constitutive trypsin in Anopheles resembles the prefeeding protease activity reported for the higher diptera, Glossina (Langley, 1967) and Sarcophaga (Capps et al, 1972). Furthermore, all mosquitoes tested so far, including aedine species (Billingsley, 1990;Billingsley and Hecker, 1991;Graf and Briegel, 1982) revealed constitutive components of aminopeptidase activity.…”