Characteristics in digestion and absorption of protein in an artificial diet in the silkworm, Bombyx mori

为了阐明家蚕（Bombyx mori）幼虫中肠膜结合氨基肽酶的生理作用，特别是在消化和吸收人工饲料中蛋白质方面的作用，本文从以下三个方面进行了研究。1)酶在中肠组织中的纵向定位2)酶纯化方法的建立3)人工饲料中蛋白质含量对酶活性的影响实验结果如下：中肠组织可分为前、中、后三部分。其中，每组织基础的活性最高的是后部分，其次是其余两个部分，活性基本相等。这说明后肠在中肠对蛋白质的消化和吸收中起着重要的作用。建立了一种纯化方法。该方法采用磷脂酰肌醇专用磷脂酶C对中肠膜部分的酶进行增溶，然后采用离子交换、金属螯合和凝胶过滤等分离介质进行柱层析。饲粮中蛋白质含量为湿重的6.4%和13.2%时，蚕蛹中肠酶活性显著高于对照组。说明该酶在高蛋白质饲粮中具有诱导作用。本研究研究了一种酶，它被认为是参与消化和吸收蛋白质的昆虫。另一种完全不同的方法是可能的，我们已经计划在短期内实现它。这是一项研究的产物分析的蛋白质消化在中肠组织，吸收多肽。如果有的话，是在中肠细胞中，如果有的话，是在这种昆虫的血淋巴中。通过对消化产物多肽的鉴定，推测了参与消化的非蛋白酶和肽酶。然后我们寻找酶。

To elucidate the physiological role of membrane-bound aminopeptidase of the larval midgut of the silkworm, Bombyx mori, especially in digestion and absorption of protein in an artificial diet, following three points were investigated. 1) longitudinal localization of enzyme in the midgut tissue, 2) Establishment of method of purification of the enzyme 3) Effect of protein content in an artificial diet on the enzyme activity.The results were as follows.1. Midgut tissue can be divided into three portions, namely, anterior, middle and posterior ones. Among them, the posterior portion was highest in activity per individual tissue basis, followed by the rest two portions with almost equal activities. This suggests that posterior portion plays a significant role in digestion and absorption of protein in the midgut.2. A purification method was established. It employs solubilization of enzyme from midgut membrane fraction using an enzyme, phosphatidylinositol specific phospholipase C, followed by column chromatographies using separationmedia of ion exchange, metal chelate, and gel filtration.3. The enzyme activity in the midgut of the silkworm larvae fed artificial diet containing protein of 6.4% and 13.2% in wet weight increased significantly compared to controls. This suggests that the enzyme is inducible upon feeding diet : with high content of protein.The present study investigated an enzyme which is supposedly involved in digestion and absorption of protein in this insect. Another completely different approach is possible and we have a plan to do it shortly. It is a study of products analysis of protein digestion in the midgut tissue, absorbed peptides. if any, in the midgut cells, and absorbed peptides, if any, in the haemolymph in this insect. By identification of peptides of digestion products, we speculate the aproteases and peptidases that were involved in digestion. Then we search for the enzymes.