Carbohydrate Digestion in Sandflies: α-Glucosidase Activity in the Midgut of Phlebotomus langeroni

Abstract

Midgut α-glucosidase (EC 3.2.1.20) activities were measured after ingestion of blood and sugar meals by the phlebotomine sandfly Phlebotomus langeroni. α-Glucosidase activity increased significantly within 1 hr after a blood meal and was maintained at significantly high activities until 48 hr postfeeding, when it fell to basal activity levels. Midgut α-glucosidase activity also increased within 1 hr of feeding on a sucrose meal, but there was no discernable peak in activity during the days postingestion. Differences in the induction of enzyme activity after a sugar meal compared to a blood meal might reflect the mode of ingestion of the two types of meal. The sugar meal is released intermittently into the midgut from the crop, in contrast to the blood meal, which is directed into the midgut immediately after ingestion and digested in a “batch” process. Nearly 90% of the α-glucosidase activity was associated with midgut cells of sugar fed sandflies compared to only 46% in blood fed insects. Isoelectrofocusing revealed the presence of seven α-glucosidases with isoelectric points between 4.3–5.8. No α-glucosidase activity was detected in the crop, indicating that glycosidases originate from the midgut epithelium rather than the salivary glands.