Theses and Dissertations

Title: Investigations on the proteolytic digestive enzymes of the channel catfish, Ictalurus punctatus (Rafinesque) and white amur, Ctenopharyngodon idella (Valenciennes)

Name: Lane, William Leeds

Degree: MS

Chair: Dr. R.T. Lovell

Resides: FAA Library

University: Auburn

Location: Auburn, Alabama

Date: 1973

Pages: 46

Keywords: Proteolytic Digestive Enzymes,Channel Catfish,White Amur.


An investigation into the production of certain proteolytic digestive enzymes in the intestine and liver of the white amur and the intestine, liver and stomach of the channel catfish was undertaken in order to provide more information on the digestive processes of these two animals. Also, a comparison of enzyme production in these two fish species was conducted taking into account seasonal and feeding variations. Substrates specifically hydrolyzed by only a certain enzyme were used in testing these organ extracts for tryptic, chymotryptic, leucine aminopeptidase and carboxypeptidase activity. Acetyl-L-tyrosine ethyl ester was used to assay for chymotrypsin, benzeyl-L-arginine ethyl ester was used to assay for trypsin, hippuryl-D,L-phenyllactic acid was used to assay for carboxypeptidase, and L-leucinamide hydrochloride was used to detect leucine aminopeptidase. Chymotrypsin, carboxypeptidase and trypsin were found to be present in the liver and intestine of the white amur and channel catfish. Leucine aminopeptidase was located in the intestine of these two fish. The liver of the channel catfish was the primary site of carboxypeptidase secretion, while the liver of the white amur seemed to play the dominant role in tryptic, chymotryptic and carboxypeptidase secretion. There appeared to be a backwash of enzymes from the intestine into the stomach of the channel catfish. There was no discernible evidence to suggest that enzyme production in either of the fish was dependent on feeding condition. Seasonal variation did, however, express effects on the level of carboxypeptidase in the liver of the channel catfish and white amur, and chymotryptic levels in the intestine of the channel catfish.

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