Mannan-degrading enzymes purified from the crop of the brown garden snail Helix aspersa Müller (Gastropoda Pulmonata).
Two mannan-degrading enzymes were purified from the crop of the terrestrial snail Helix aspersa Müller. The crude extracts were taken from dormant (for 4 months) snails. The enzymes were a betaD-mannanase of 37.4 +/- 0.3 kDa (EC 3.2.1.78) and a betaD-mannosidase of 77.8 +/- 1.9 kDa (EC 3.2.1.25). Both enzymes degraded insoluble mannan, releasing either mannose only (beta-mannosidase) or oligosaccharides, possibly mannotriose and mannopentaose (beta-mannanase). The beta-mannanase had a typical endo-activity pattern, while the beta-mannosidase was an exoenzyme. The incubation of both enzymes with mannan increased the catalysis by 83%. The best synergy was found with 75% mannosidase combined with 25% mannanase. The beta-mannanase also hydrolysed beta-linked heteromannans and its affinity for different galactomannans was studied. The Km values, varying from 2.89 +/- 0.47 mg x ml(-1) to 0.26 +/- 0.01 mg x ml(-1), revealed the inhibitory effect of the alphaD-galactosyl residues released. The beta-mannosidase was acidic (optimum pH = 3.3) and heat-sensitive (50% residual activity at 42 degrees C after 5 min of pre-incubation), while the beta-mannanase remained stable until 48.5 degrees C (50% residual activity) and over a pH range of 4.3-7.5. The properties of these mannanolytic enzymes are discussed in this paper compared with those purified in other gastropods and in a bacterium, Enterococcus casseliflavus, a quite similar strain previously isolated from this snail intestine. The occurrence of thermostable enzymes in H. aspersa digestive tract could be a zootechnic parameter of great importance for snail farming. J. Exp. Zool. 290:125-135, 2001.
Charrier
M
M
Equipe de Physiologie et d'Ecophysiologie, UMR EcoBio 6553, Campus de Beaulieu, 263 Avenue du Général Leclerc, 35042 Rennes, France. Maryvonne.Charrier@univ-rennes1.fr
Rouland
C
C
D000818:Animals; D016983:Enterococcus / Q000201:enzymology; D006372:Helix, Snails / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008351:Mannans / Q000378:metabolism*; D008361:Mannosidases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature; D044902:beta-Mannosidase
D008351:Mannans; D008361:Mannosidases; D044902:beta-Mannosidase