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First published online October 21, 2004
Journal of Experimental Biology 207, 4095-4104 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01252

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Presence and properties of cellulase and hemicellulase enzymes of the gecarcinid land crabs Gecarcoidea natalis and Discoplax hirtipes

Stuart M. Linton^* and Peter Greenaway

School of Biological, Earth and Environmental Sciences, The University of NSW, Sydney, NSW 2052, Australia

^* Author for correspondence at present address: School of Biological and Chemical Sciences, Faculty of Science and Technology, Deakin University – Geelong Campus, Pigdons Road, Geelong, VIC 3217, Australia (e-mail: stuart.linton{at}deakin.edu.au)

Accepted 18 August 2004

Digestive juice from the herbivorous gecarcinid land crabs Gecarcoidea natalis and Discoplax hirtipes exhibited total cellulase activity and activities of two cellulase enzymes; endo-ß-1,4-glucanase and ß-1,4-glucosidase. These enzymes hydrolysed native cellulose to glucose. The digestive juice of both species also contained laminarinase, licheninase and xylanase, which hydrolysed laminarin, lichenin and xylan, respectively, to component sugars. The pH optima of ß-1,4-glucosidase, endo-ß-1,4-glucanase and total cellulase from G. natalis were 4–5.5, 5.5 and 5.5–7, respectively. In the digestive juice from D. hirtipes, the corresponding values were 4–7, 5.5–7 and 4–9, respectively. The pH of the digestive juice was 6.69±0.03 for G. natalis and 6.03±0.04 for D. hirtipes and it is likely that the cellulases operate near maximally in vivo. In G. natalis, total cellulase activity and endo-ß-1,4-glucanase activity were higher than in D. hirtipes, and the former species can thus hydrolyse cellulose more rapidly. ß-1,4-glucosidase from G. natalis was inhibited less by glucono-D-lactone (K_i=11.12 mmol l^-1) than was the ß-1,4-glucosidase from D. hirtipes (K_i=4.53 mmol l^-1). The greater resistance to inhibition by the ß-1,4-glucosidase from G. natalis may contribute to the efficiency of the cellulase system in vivo by counteracting the effects of product inhibition and possibly dietary tannins. The activity of ß-1,4-glucosidase in the digestive juice of D. hirtipes was higher than that of G. natalis.

Key words: land crab, Gecarcoidea natalis, Discoplax hirtipes, cellulase, endo-ß-1, 4-glucanase, cellobiohydrolase, ß-1, 4-glucosidase, laminarinase, xylanase, licheninase, fibre digestion

This article has been cited by other articles:

				B. J. Allardyce and S. M. Linton Purification and characterisation of endo-{beta}-1,4-glucanase and laminarinase enzymes from the gecarcinid land crab Gecarcoidea natalis and the aquatic crayfish Cherax destructor J. Exp. Biol., July 15, 2008; 211(14): 2275 - 2287. [Abstract] [Full Text] [PDF]