Digestive peptidases in Tenebrio molitor and possibility of use to treat celiac disease

Digestion in Tenebrio molitor larvae occurs in the midgut, where there is a sharp pH gradient from 5.6 in the anterior midgut (AM) to 7.9 in the posterior midgut (PM). Accordingly, digestive enzymes are compartmentalized to the AM or PM. Enzymes in the AM are soluble and have acidic or neutral pH optima, while PM enzymes have alkaline pH optima. The main peptidases in the AM are cysteine endopeptidases presented by two to six subfractions of anionic proteins. The major activity belongs to cathepsin L, which has been purified and characterized. Serine post‐proline cleaving peptidase with pH optimum 5.3 was also found in the AM. Typical serine digestive endopeptidases, trypsin‐like and chymotrypsin‐like, are compartmentalized to the PM. Trypsin‐like activity is due to one cationic and three anionic proteinases. Chymotrypsin‐like activity consists of one cationic and four anionic proteinases, four with an extended binding site. The major cationic trypsin and chymotrypsin have been purified and thoroughly characterized. The predicted amino acid sequences are available for purified cathepsin L, trypsin and chymotrypsin. Additional sequences for putative digestive cathepsins L, trypsins and chymotrypsins are available, implying multigene families for these enzymes. Exopeptidases are found in the PM and are presented by a single membrane aminopeptidase N‐like peptidase and carboxypeptidase A, although multiple cDNAs for carboxypeptidase A were found in the AM, but not in the PM. The possibility of the use of two endopeptidases from the AM – cathepsin L and post‐proline cleaving peptidase – in the treatment of celiac disease is discussed.     

Protein Bodies from Buckwheat Seed Cotyledons: Isolation and Characteristics

Protein bodies were isolated from cotyledons of dry buckwheatseeds by homogenization in acetone with subsequent purificationin a 1.26 g cm^–3 to 1.53 g cm^–3 linear density gradientof a mixture of acetone with CCI₄. The purified fraction ofprotein bodies with globoids (PB I) had a buoyant density of1.48–1.51 g cm^–3 and was intact according to microscopicdata. Localization of hydrolytic enzymes and proteinase inhibitorsin the PB I fraction and in the fraction of the cytoplasm andmembrane material (CMM) was studied. It was shown that acidhydrolytic enzymes, such as aspartic proteinase, carboxypeptidase,acid phosphatase, -D-mannosidase and N-acetyl-ß-glucosaminidase,as well as chymotrypsin and trypsin inhibitors were predominantlylocalized in the PB I. BAPAase and SH-activated caseinase activitieswere equally distributed between the PB I and CMM fraction.The activities of leucine aminopeptidase and SH-independentcaseinase were noticeably predominant in the CMM fraction. Key words: Buckwheat, subcellular fractionation, protein bodies, hydrolases