1997 年 32 巻 4 号 p. 533-540
The colepteran-active δ-endotoxin of Bacillus thuringiensis serovar japonensis strain Buibui had a so-called proteinase-resistant region of 50 kDa which is resistant to trypsin and larval midgut-juice of Bombyx mori. However, the δ-endotoxin of strain Buibui was degraded to smaller polypeptides of less than 20 kDa by larval midgut-juice of Anomala cuprea. In addition, the CryIAa δ-endotoxin was also degraded to smaller polypeptides by the midgut-juice. On the other hand, a mixture of trypsin and autoclaved A. cuprea midgut-juice degraded the δ-endotoxin to smaller polypeptides but the autoclaved midgut-juice with Staphylococcus aureus V8 proteinase or lysyl endopeptidase did not. These results suggest that A. cuprea midgut-juice may have a high activity to digest the δ-endotoxins, for which a trypsin-like proteinase may play an important role. Moreover, A. cuprea ;midgut-juice may contain a factor(s) which cooperates with trypsin to digest δ-endotoxin into smaller polypeptides.
