Page 52 - Enzymes in Tropical Soils

40 Enzymes In Tropical Soils

and the rest is adsorbed on soil solids. The soluble enzyme is the active part that
participates in the transformation of organic nutrient elements to become
inorganic nutrient elements.
Geiger et al. (1998a) state that most extracellular enzymes are adsorbed on
organic and mineral constituents. Gianfreda et al. (1992) reported that the
equilibrium adsorption of urease on clay minerals fitted the Langmuir and
Freundlich equations. Huang et al. (2005) reported that in the presence of organic
component, more enzyme molecules were adsorbed on soil clays which were more
easily released. The activity of enzymes bound on soil clays was inhibited by the
presence of organic matter. Coarse clays (0.2–2 mm) and inorganic soil clays had
higher affinities for enzyme molecules than fine clays and organic clays,
respectively. Dharmakeerti and Thebadu (1996) states that urease is remarkably
stable in organo-mineral complexes found in soils.

L-H

Soil Depth (cm) 15-30 Jordan River
0-5
.5-15

30-60 Shawnigan Lake

0 1000 2000 3000
Activity
-1
-1
(mg p-Nitrophenol g h )

Fig. 4.4. The depth dependence of soil phosphomonoesterase activity
(Redrawn from Pang and Kolenko, 1986).

Sarkar et al. (1989) reported that various enzymes including glucose oxidase,
-glucosidase, acid phosphatase, tyrosinase, and laccases were immobillized on
clays and soils and retained a large amount of their original activities after

Abdul Kadir Salam - 2014