Catalase, protease and urease activity in some types of soil

Enzymes in the soil are closely related to the physical, chemical and biological characteristics of the soil and regulate the formation of soil fertility, organic matter, nutrient mineralization and cycling in nature. Soil contains phosphatase, urease, dehydrogenase, catalase, peroxidase, saccharase, protease, amylase, β-glucosidase, arylsulphatase and other enzymes. The purpose of the given work was estimation of catalase protease and urease activity on three different types of soil as high mountained steppe and dry steppe roughly humusified soil; mealy brown carbonated soil and mountain meadow forest soil which are common in the mountain and steppe regions of our country in correlation with soil depth and anthropogenic impacts. In all soil samples the highest enzymatic activities were detected in the depth of 0-15 cm from the soil surface. For all soil samples the enzymes activities decreased more rapidly with increasing soil depth affected to anthropogenic impacts in comparison with samples not exposed to human impacts.


INTRODUCTION
nzymes in soils mainly come from plants, soil animals and microorganisms and connected covalently, crosslinked, copolymerized, adsorbed and included in the microcapsules of soil particles (Girish S., Ajit V., 2011).Soil enzyme activities vary seasonally and have been related to soil physiсo-chemical characters, microbial community structure, vegetation, disturbance and succession (Caldwell B. A. (2005).That is why soil enzymes play an important role in formation, converting and decomposition of organic matter to the plant digestible forms, decomposition of xenobiotics, involved in the nitrogen and other elements cycle and life cycling of soil microorganisms (Schaller K., 2009).Nowaday soil enzyme activities have been used as indicators in evaluation of soil quality, climate changes, destruction and toxification in ecosystems.Protease (EC 3.4.4…) in soil plays a significant role in nitrogen mineralization, more active in soils with a high water and humus content forest soils and landfills.Activity of this enzyme does not depend on microbial community of soils and expresses the biological activity of the soil.The enzyme associated with soil fertility, regulating the amount of available nitrogen in plant and plant growth.(Girish S.et al., 2011).Peroxide in soil is formed during respiration and oxidation of organic matter (Andersen D.W., Gregorich E.G., 1980).Catalase (EC 1.11.1.6)decomposes peroxide and its activity depends from organic oxygen concentration, microbe biomass, changes in CO 2 , and depends from dehydrogenase, amidase, glucosidase and esterase activity in soils.Therefore an important indicator of soil fertility and aerobic microorganisms (Burns R.G., 1982).Urease (EC 3.5.1.5)activity in soils depends from organic and inorganic matter content; especially urease is very sensitive to heavy metals (Girish S.et al., 2011).

EXPERIMENTAL
Three types of soils samples were used in our study (table 1).In all soil samples moisture, soluble protein, protease, catalase and urease activities were estimated.

E
The moisture was estimated gravimetrically, protein contents -by the Beneduct method (Kochetov G.A., 1980), the protease activityby Kunitz M. method, catalase -by method Bach A.N. and Zubkova S.M. and the urease activity -by the Porter L. K., methods (Purev D. Bayarmaa J., 2012).Enzymatic activities were expressed in units. 1 unit of catalase activity was taken as 1mg of hydrogen peroxide hydrolyzed by catalase of 1g soil in 1 hour, 1 unit of protease activity was taken as 1μg of tyrosine formed in 1g of soil in 1 hour and 1 unit of urease activity was taken as 1μg of urea hydrolyzed by urease of 1g soil in 1 hour.

RESULTS AND DISCUSSION
Samples of three different types of soil as high mountained steppe and dry steppe roughly humusified soil; mealy brown carbonated soil and mountain meadow forest soil with and without human impact were collected from the depth of 0-7, 7-15 and 15-25 cm from the soil surface in June 2011 and used in our study.In all samples moisture, protein content, the protease, catalase and urease activities were estimated.Results are summarized in tables 2, 3 and 4.
As we see from the table 2 high in mountained steppe and dry steppe roughly humusified soil, mealy brown carbonated soil and mountain meadow forest soils the moisture content decreases to the soil depth of 1.14-2.10times.About soluble protein content it has a tendency to decrease to the soil depth to (decreases 1,29-3 times to the soil depth).It can be seen from the calculation of the correlation coefficient (table 2).The protein content decreases from high mountained steppe and dry steppe roughly humusified soil > mountain meadow forest soil > mealy brown carbonated soils which shows that the protein content has a dependence from the soil type.
From the table 3 we can see that the activity of estimated enzymes have a dependence from the soil depth.In all soil samples estimated enzymes have the highest activity at a depth of 0-15 cm from the soil surface.Rapid decreasing trend for estimated enzymes activities with increasing depth of soil for all soil samples affected to human impacts in comparison with samples not exposed to human impacts were observed (table 3).