title: Why bluefin tuna have warm tummies: temperature effect on trypsin and chymotrypsin.
abstract: Giant bluefin tuna warm their viscera during and after a meal. The cecum of a 500-kg bluefin weighs about 9 kg and contains about 20,000 pyloric ceca, each about 10 cm long and 1.5 mm diam. Trypsin was assayed with alpha-benzoyl-DL-arginine-p-nitroanilide HCl and chymotrypsin with glutaryl-L-phenylalanine-p-nitroaniline. The effects of pH on specific activity over the range 7.5-9.5 were negligible relative to temperature effects. Specific activity and maximal reaction velocity extrapolated from a Lineweaver-Burke plot (Vmax) increased with an increase in temperature in a similar fashion (Q10 ca. 2 over temperature range of physiological significance), whereas Km was constant over the same temperature range. The advantage of the warm cecum is that protein is digested in about one-third the time, so that these tuna can process about three times as much food per day.
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation; D002432:Cecum / Q000201:enzymology; D002918:Chymotrypsin / Q000378:metabolism*; D005399:Fishes / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013696:Temperature; D014357:Trypsin / Q000378:metabolism*; D014413:Tuna / Q000502:physiology*
chemical_list: D002918:Chymotrypsin; D014357:Trypsin