Occurrence of a cathepsin B-like acid cysteine proteinase in the eggs of silkworm moth, Antheraea pernyi

Nutritional aspects and dietary benefits of "Silkworms": Current scenario and future outlook

In the current scenario, it is estimated that by 2050, there will be an additional 2.5 billion people and a 70% increase in food demand. Crop yields are not increasing fast enough to support global needs, and world agriculture is facing several serious challenges. Therefore, insects can be a nutritious alternative to meet the ever-increasing food demand in the present and future. The majority of insect consumption occurs in developing countries, with approximately 1,900 insect species consumed worldwide. Food and feed derived from them are of high quality, have a high feed conversion ratio and emit a low level of greenhouse gases. Among insects silkworms are beneficial to humans, not only because of their high nutritional value, but also because of their several pharmacological properties. Silkworm eggs, larvae, and pupae contains high amount of proteins, oils, minerals, vitamins, and several other beneficial components which are nutritious as well as have positive effect on human health. Studies have shown that silkworm pupae protect the liver, enhance immunity, inhibit apoptosis, inhibit cancer, inhibit tumor growth, inhibit microbial growth, regulate blood glucose and blood lipids, and lower blood pressure. This review paper summerized the nutritional value of different life stages of silkworm, nutritional comparison of silkworm with the major human foods, and the effects of silkworm consumption on human health, thus ittargets to generate interest toward in sericulture and improve human health by using silkworm as a nutritious food and attain sustainability in food and nutritional security.

Cathepsins of lepidopteran insects: Aspects and prospects

Molecular understanding of lepidopteran physiology has revealed that proteases consist of one of the central regulatory/reacting system for insect growth and survival. Among the various proteases, cathepsins are the most crucial cellular proteases, which play vital roles during insect development. In the present review, we have discussed various aspects of the lepidopteran insect cathepsins, emphasizing their roles in processes like development, growth, metamorphosis, apoptosis and immunity. Cathepsins are categorized into different types on the basis of their sequence diversification, leading to variation in structure and catalytic function. Cathepsins exhibit tissue and stage specific expression pattern which is fine-tuned by a delicate balance of expression, compartmentalization, zymogen activation, inhibition by protein inhibitors and degradation. The indispensability of cathepsins as cellular proteases in the above mentioned processes proposes them as novel targets for designing effective and specific insect controlling strategies.

Potential role of cathepsin B in the embryonic and larval development of clam Meretrix meretrix

This study was designed to investigate the possible role of Meretrix meretrix cathepsin B (MmeCB) in embryonic and larval development. MmeCB mRNA expression profile was revealed by semi-quantitative RT-PCR. The level of MmeCB mRNA expression was low in trochophore stage but high in pedveliger stage. MmeCB protein expression was detected in the digestive gland, velum, and epidermis along the edges of the shell in D-larvae and pedveligers by immunocytochemistry. In post larvae, MmeCB protein expression was noticed abundant in the digestive gland, whereas a modest expression was identified in the gill filament. The average shell length of larvae hatched from embryos treated with 0.01, 1, and 10 µmol/L Ca074Me (a cathepsin B inhibitor) was significantly shorter than that of control groups. The metamorphosis rates of larvae treated with 0.01 and 1 µmol/L Ca074Me were significantly lower than that of control groups in 4-day larvae, but not in 5-day larvae. Taken together, these results indicated that MmeCB may have stimulatory effects on embryonic development, metamorphosis, and larval growth during M. meretrix larval development.

Preoviposition activation of cathepsin-like proteinases in degenerating ovarian follicles of the mosquito Culex pipiens pallens

Within developing ovaries of many insects, some developing follicles or oocytes usually degenerate (follicular atresia or oosorption), while the others may continue to grow to maturity, thus maintaining the balance between the number of eggs and reproductive circumstances such as available nutrients. To help clarify the phenomenon of follicular atresia during ovarian development, we examined cysteine proteinases stored in mosquito Culex pipiens pallens ovaries. First, analysis using synthesized substrates showed that cathepsin B- and L-like proteinases gradually accumulated in the developing ovaries after a blood meal, which required more than 10 min of preincubation under acidic conditions to reach their maximum activities. However, homogenates of degenerating follicles 3 days after feeding showed proteolytic activities without acid treatment, suggesting that the proteinases had already been activated, while the extract of normally developing follicles collected from the same ovaries required more than 10 min of acid preincubation to reach the optimum activities, suggesting that the enzymes remained as inactive forms. Chemical and immunohistochemical analyses showed that more proteinases are located in the cytoplasm, rather than being associated with yolk granules. Ovarian proteinases, which are believed to become activated at the onset of embryogenesis, should also be activated during oogenesis, presumably to enhance oosorption.

Miltpain, new cysteine proteinase from the milt of chum salmon, Oncorhynchus keta

A new cysteine proteinase, salmon miltpain, was isolated and purified from the milt of chum salmon (Oncorhynchus keta). Native molecular mass was estimated as 67,000 by gel filtration column chromatography (Shodex WS2003) and 22,300 by SDS-polyacrylamide gel electrophoresis. Isoelectoric point was determined to be 3.9 by isoelectric focusing. The first 15 amino acid residues in the N-terminal region were LPSFLY-AEMVGYNIL. The cysteine proteinase, which had a pH optimum of 6.0 for Z-Arg-Arg-MCA hydrolysis, required a thiol-reducing reagent for activation and was inhibited by E-64, iodacetamide, CA-074 Me, TLCK, TPCK and ZPCK. The cysteine proteinase exhibited unique substrate specificity toward paired basic residues such as Lys-Arg, Arg-Arg at the subsites of P2-P1 and had a K(m) of 16.3 microM and kcat of 20.3 s-1 with Z-Arg-Arg-MCA as substrate and a K(m) of 52.9 microM and kcat of 1.79 s-1 with Z-Phe-Arg-MCA. This proteinase was found to considerably hydrolyze basic proteins such as histone, salmine and clupaine but not milk casein.