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The flow and fate of digestive enzymes in the field cricket, Gryllus bimaculatus
Author(s) -
Woodring Joseph
Publication year - 2017
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.21398
Subject(s) - gryllus bimaculatus , maltase , biology , amylase , trypsin , midgut , biochemistry , hindgut , enzyme , lipase , digestive enzyme , digestion (alchemy) , disaccharidase , chymotrypsin , chemistry , chromatography , botany , cricket , larva , ecology
The flow of enzymes, the ratio of bound to unbound enzymes, and their inactivation in the cricket Gryllus bimaculatus was studied. The digestive enzymes are forced forward into the crop by caecal contraction and then they are mixed with freshly chewed food and saliva, forming a crop‐chyme. This chyme is blended by crop peristalsis, and periodic opening of the preproventricular valve (PPV) allows posterior movement into the proventriculus and further into the midgut. The contraction of the crop is modulated by Grybi‐AST and Grybi‐SK peptides, which are partially secreted by the caecal endocrine cells. Most of the aminopeptidase and the four disaccharidases examined are membrane bound (62–80%); the remaining (20–38%) as well all trypsin, chymotrypsin, lipase, and amylase are secreted free into the caecal lumen. Cricket trypsin loses only 30% of its activity in 4 h and very little thereafter. The presence of digestive products in the lumen appears to retard further trypsin autolysis. Cricket trypsin digests 42% of the chymotrypsin, 37% of the lipase, and 45% of the amylase in the caecal fluids over 24 h in vitro no significant difference. Without Ca ion amylase was almost completely digested. About 50% of the membrane bound and free aminopeptidase was digested in the caecal lumen, and about 30–38% of the bound and free maltase. This loss of digestive enzyme activity is possible, because enzyme secretion rates are high, the unbound enzymes are effectively recycled, and the time of nutrient passage is short.