| This article summarizes the research progress of fish's digestive enzymes and explores the characters of digestive enzymes in turbot from the biological angle. Four questions are discussed in this paper. (1) the distribution and optimum temperature and pH of digestive enzymes in turbot (2) the effects of main chemical reagents on the activity of digestive enzymes in turbot (3) the separation of digestive enzymes in turbot through native-PAGE (4)the activity changes of digestive enzymes in turbot at different growth stages. The results are as follows:l.List the optimum temperature correspondent with pH of different parts in the alimentary tract (stomach, pylorus, foregut, midgut, hindgut), and under moderate conditions, rank the activity of digestive enzymes from high to low, (1) Protease -40℃ 2.0 , 40℃ 8.0 , 60℃ 8.0 , 40℃ 8.5 , 60℃ 8.0; pylorus > stomach > foregut > midgut > hindgut (2) Amylase -40℃ 6.5 , 40℃ 8.0 , 40℃ 7.5 , 50℃ 7.0 , 40℃ 8.0; pylorus > foregut > midgut > hindgut > stomach (3) Lipase -40℃ 7.5 ,40℃ 6.5 ,40℃ 7.0; foregut > midgut > pylorus > hindgut > stomach2. This paper deals with the effects of EDTA , NaCl and eleven kinds of metal ions on stomach protease, foregut protease, pylorus amylase, and foregut lipase. The results demonstrate that: the protease is activated by Ca2+ ,Mg2+ , Fe3+; inhibited by Cu2+, Hg2+, Ag+; scarcely influenced by EDTA and NaCl. The amylase is activated by Ca2+ , Mn2+;inhibited by EDTA, NaCl , Cu2+, Zn2+ ,Cd2+ ,Pb2+,Hg2+ and Mg2+. The lipase is activated by NaCl, K+ ,Ca2+;inhibited by Cu2+, Mg2+, Fe3+, H.g2+, Zn2+, Pb2+, Cd2+,Ag+andMn2+.3. The digestive enzymes in turbot are separated and analysed through native-PAGE. (1) Glutin digestion in situ is applied to protease. Under acid conditions, six zymograms are separated from stomach protease, in which there are one bright band, two mid-bright bands and three dim bands. Four zymograms are tested from pylorusprotease; two bright bands, one mid-bright band and one dim band. Foregut protease is composed of three bands, two bright bands and one dim band, what's more three zymograms are at the same molecular weight level with pylorus protease's front three bands only with lower activity. Midgut protease includes two dim bands, whose first band parallels hindgut protease's one dim band. (2) Isozyme technology is applied to amylase. Stomach amylase has one mid-bright band. Pylorus amylase has four bands, three bright ones and one dim band. Foregut amylase has one mid-bright band and one dim band. Midgut and hindgut amylase each have one dim band. Stomach ,midgut and hindgut's band are consistent with pylorus and foregut's second band. (3) Isozyme technology is still used to lipase. One bright band, one mid-bright band and two dim ones are found from stomach lipase, which is similar to pylorus lipase. Foregut lipase comprises two bright bands, one mid-bright band and two dim ones. Midgut lipase consists of One bright band, two mid-bright bands and two dim ones. Hindgut lipase has the same bands as midgut lipase only with lower activity. The first band of different digestive parts has similar molecular weight.4. The category and activity of turbot's digestive enzymes change with the growth. The activity of protease takes an ascending trend and reaches the top at 2 years old. There lies in difference in respective growth phase, rising fasted from 30 days old to 90 days old, increasing slower from 90 days old to 1 year old , changing little from 1 year old to 2 year old. The activity of amylase goes up at first, then followed with an decrease. It increases fasted from 30 days old to 90 days old, then ascends slower. The activity of lipase mounts gradually and arrives at the peak when at 2 years old. |
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