Trehalose is the main haemolymph sugar in most insects including the tobacco hornworm, Manduca sexta, and is potentially a prime target for an invading pathogenic fungus. There was considerably more trehalose-hydrolysing activity in the haemolymph of caterpillars infected with Metarhizium anisopliae than in controls. This appeared to be due primarily to additional isoforms; one of which could also hydrolyse maltose and was designated an a-glucosidase. A comparable isoform was identified in in vitro culture of the fungus, supporting a fungal origin for the in vivo enzyme. The in vitro fungal enzyme, a-glucosidase-1 (a-gluc-1), was purified to homogeneity and partially characterised. A study with the trehalase inhibitor trehazolin and C14 trehalose suggested that extracellular hydrolysis is important for fungal mobilisation of trehalose. Haemolymph glucose increases significantly during mycosis of tobacco hornworm larvae by M. anisopliae, consistent with the hydrolysis of trehalose by extracellular fungal enzymes. The implications for the host insect are discussed.

A comparison has been made between the effects of wounding, chemical stimulation of the immune system and fungal infection on acid phosphatase (AcP) activity in the haemolymph of the desert locust, Schistocerca gregaria. Untreated control locusts had constitutive levels of AcP. As a lysosomal enzyme, AcP may have a role in autophagy and cell turn over as well as defence. Injection of saline and b-1,3-glucan caused significant increases in haemocyte and plasma AcP. AcP activity also increased in the haemolymph on the 3rd day after inoculation with the entomopathogenic fungus M. anisopliae var acridum. This coincided with a decline in the total haemocyte count and a marked reduction in the proportion of plasmatocytes and coagulocytes that stained positive for AcP. Therefore a priori it seemed unlikely that the extra AcP in infected insects came from the host. A fungal origin for the enzyme was suggested by the identification of AcP isoforms from haemolymph of different treatments. Control inoculated (oil only) insects had an AcP at a pI of 4.3 that was stimulated further by the injection of laminarin. Additional isoforms appeared at around 7.3–7.5 in the laminarin treatment. However, the 4.3 isoform appeared to be suppressed in the insects infected with M. anisopliae var acridum. The band intensity was more like that of the control than the laminarin-injected insects. Two new isoforms appeared later on in infection. These enzymes had pIs that corresponded to some of the AcPs produced in vitro by the fungus. The results are discussed in the light of the possible benefits of secreted fungal acid phosphatases to the pathogen.

综述了植物蛋白酶抑制剂抗虫与抗病作用的研究进展。蛋白酶抑制剂广泛存在于植物体内，与植物抗虫抗病密切相关。植物蛋白酶抑制剂能抑制昆虫肠道蛋白酶，使昆虫生长发育缓慢，甚至死亡。但取食蛋白酶抑制剂后，昆虫能迅速分泌对抑制剂不敏感的蛋白酶，而使蛋白酶抑制剂无效。食物蛋白的含量和质量也影响植物蛋白酶抑制剂的抗虫效果。病原菌的感染能诱导植物产生蛋白酶抑制剂，诱导产生的蛋白酶抑制剂能抑制病原菌的生长。

以几丁质为底物，加入基本盐培养基中，诱导球孢白僵菌（Beauveria bassiana）产生分解昆虫表皮的蛋白酶。诱导物中，蝉蜕诱导的蛋白酶总活性、比活较高，经超滤、离子交换层析、亲和层析、制备性IEF电洗脱纯化了一种有凝乳弹性蛋白酶（Prl）活性的蛋白酶BbPrl。经SDS-PAGE电泳银染后呈单带，HILC凝胶过滤显示单峰。BbPrl为单体酶，分子量为33.6kD左右，pI为7.4。底物专一性测定显示，BbPrl能水解Phe或ku形成的酰胺键和肽键。BbPrl可被PMSF抑制，表明其活性中心有Ser残基；BbPrl还可被胰凝乳蛋白酶抑制剂TPCK和凝乳弹性蛋白酶抑制剂TEI等所抑制；胰蛋白酶抑制剂LeupepUin和Epianstatin，及胃蛋白酶抑制剂Pepstain对BbPrl活性无影响。还研究了BbPrl的最适作用pH和pH稳定性。