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Table 1.

The effect of pH on the activity of cellulase enzymes from the foregut of the gecarcinid crabs Gecarcoidea natalis and Discoplax hirtipes

Activity (μmol min-1 ml-1 digestive juice)
EnzymepH 4pH 5.5pH 7pH 8pH 9
Total cellulase      
   G. natalis 0.018±0.016a 0.043±0.016b 0.017±0.010a 0.021±0.020a 0.011±0.011a 
   D. hirtipes 0.014±0.005a 0.020±0.005a 0.023±0.006a 0.005±0.002a 0.010±0.003a 
β-1,4-glucosidase      
   G. natalis 0.397±0.253a,b 0.521±0.253a 0.254±0.131b,c 0.075±0.032c,d 0.031±0.019d 
   D. hirtipes 1.779±0.083a 1.729±0.066a 1.961±0.074a 0.214±0.046b 0.121±0.028b 
Endo-β-1,4-glucanase      
   G. natalis 0.297±0.174a 2.076±0.104b 2.304±0.116b 0.945±0.189c 1.981±0.106b 
   D. hirtipes 0.627±0.092a 1.534±0.206b 1.434±0.101b 0.710±0.169a 1.041±0.151a,b 
Activity (μmol min-1 ml-1 digestive juice)
EnzymepH 4pH 5.5pH 7pH 8pH 9
Total cellulase      
   G. natalis 0.018±0.016a 0.043±0.016b 0.017±0.010a 0.021±0.020a 0.011±0.011a 
   D. hirtipes 0.014±0.005a 0.020±0.005a 0.023±0.006a 0.005±0.002a 0.010±0.003a 
β-1,4-glucosidase      
   G. natalis 0.397±0.253a,b 0.521±0.253a 0.254±0.131b,c 0.075±0.032c,d 0.031±0.019d 
   D. hirtipes 1.779±0.083a 1.729±0.066a 1.961±0.074a 0.214±0.046b 0.121±0.028b 
Endo-β-1,4-glucanase      
   G. natalis 0.297±0.174a 2.076±0.104b 2.304±0.116b 0.945±0.189c 1.981±0.106b 
   D. hirtipes 0.627±0.092a 1.534±0.206b 1.434±0.101b 0.710±0.169a 1.041±0.151a,b 

Total cellulase and β-1,4-glucosidase activities were measured as the rate of glucose production from the hydrolysis of either crystalline cellulose or cellobiose, respectively. Endo-β-1,4-glucanase activities were measured as the rate of reducing sugars produced from the hydrolysis of carboxymethyl cellulose. Within a row, similar superscript letters indicate similar means (P>0.05). Values are means ± s.e.m. (N=10).

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