Cathepsin B-Like Protease Expression In Hemocytes Of Cotton Boll Worm Larvae

Proteases are the enzymes that hydrolyze proteins or peptides. There are many kinds of protease that distribute widely among animals, plants and microorganism. Usually, proteases play important roles in metabolism and biological regulation of various organisms. Proteases are categorized as endopeptidases (EC3.4 21-24, 99) and exopeptidases (EC3.4 11-19) according to their cleavage sites on target peptides. Endopeptidases are further divided into serine endopeptidases, cysteine endopeptidases, aspartic endopeptidases and metalloendopeptidases based on the chemical characteristics or amino acids in the catalytic centers.Among these proteases, cathepsins (Cath.) are a large group of enzymes which are more important to life activities of organisms. Cathepsins can be activated under acid circumstance. Cathepsins normally exist in lysosomes, and can non-specifically degrade stock proteins into amino acids to supply the cells with amino acids for energy and glucose as needed. Cathepsins can also take part in many other physiological processes across species. Such as bone resorption and programmed cell death. If cathepsins expressed abnormally, it can invoke pathological reactions, for example, degradation of extracellular matrix (ECM) proteins by cathepsins is required for tumor cell invasion and metastasis.Cathepsins have also been reported in numerous insects, most important of them are Cath.B, Cath.D and Cath.L. Insect cathepsins mainly distribute in fat bodies, mid gut and hemocytes of larvae, early embryos and oocytes. They can play various roles in insect life processes, such as oogenesis, embryonic development, food digestion and histolysis and histogenesis during metamorphosis.The cotton boll worm, Helicoverpa armigera is belonged to Lepidoptera: Noctuidae, and is a kind of widely distributed and harmful pest. In previous work, cathepsin B-like protease had been purified and its gene had been cloned from the cotton boll worm, named H. armigera cathepsin B (HCB; EC 3.4.22.1; GenBank AF222788). HCB is a cysteine proteinase. Pro-HCB is a 37 kDa protein and mature...