Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Brazil.
J Insect Physiol. 2012 Oct;58(10):1314-24. doi: 10.1016/j.jinsphys.2012.07.005. Epub 2012 Jul 25.
Lutzomyia longipalpis is the principal species of phlebotomine incriminated as vector of Leishmania infantum, the etiological agent of visceral leishmaniasis in the Americas. Despite its importance as vector, almost nothing related to the larval biology, especially about its digestive system has been published. The objective of the present study was to obtain an overview of carbohydrate digestion by the larvae. Taking in account that phlebotomine larvae live in the soil rich in decaying materials and microorganisms we searched principally for enzymes capable to hydrolyze carbohydrates present in this kind of substrate. The principal carbohydrases encountered in the midgut were partially characterized. One of them is a α-amylase present in the anterior midgut. It is probably involved with the digestion of glycogen, the reserve carbohydrate of fungi. Two other especially active enzymes were present in the posterior midgut, a membrane bound α-glucosidase and a membrane bound trehalase. The first, complete the digestion of glycogen and the other probably acts in the digestion of trehalose, a carbohydrate usually encountered in microorganisms undergoing hydric stress. In a screening done with the use of p-nitrophenyl-derived substrates other less active enzymes were also observed in the midgut. A general view of carbohydrate digestion in L. longipalpis was presented. Our results indicate that soil microorganisms appear to be the main source of nutrients for the larvae.
长刺舌蝇是美洲内脏利什曼原虫的主要传播媒介，是被怀疑的舌蝇种类。尽管它作为传播媒介很重要，但几乎没有关于其幼虫生物学的信息，特别是关于其消化系统的信息。本研究的目的是获得幼虫对碳水化合物消化的概述。考虑到舌蝇幼虫生活在富含腐烂物质和微生物的土壤中，我们主要寻找能够水解这种底物中存在的碳水化合物的酶。中肠中遇到的主要糖基水解酶被部分表征。其中一种是存在于前中肠的α-淀粉酶。它可能参与真菌糖原的消化，糖原是真菌的储备碳水化合物。在后中肠中还存在另外两种特别活跃的酶，一种是膜结合的α-葡萄糖苷酶和一种膜结合的海藻糖酶。前者完成糖原的消化，后者可能在遇到水胁迫的微生物的海藻糖消化中起作用。在使用对硝基苯衍生底物进行的筛选中，中肠中还观察到其他活性较低的酶。本文提出了长刺舌蝇碳水化合物消化的总体概况。我们的结果表明，土壤微生物似乎是幼虫营养物质的主要来源。
