This study was conducted to determine how cultivation influences the activity and diversity as well as kinetic and thermodynamic parameters of soil cellulase in three ecosystems including forest, rangeland, and saline desert soils. Land use change effects on the amount and diversity of soil proteins were also studied. Soil samples were collected in October 2009 from a native forest, a native rangeland, and a native saline desert as well as adjacent cultivated fields in central Iran. Land use changes not only decreased the amount of soil proteins but also influenced the protein pattern. Soil protein content decreased by 64%, 55% and 90% in the cultivated sites, as compared with their corresponding native forest and native rangeland sites, respectively. Electrophoretic patterns of soil proteins from agricultural soils were clearly different from those of the native lands. Cultivation of the native forest, rangeland, and saline desert soils resulted in 79%, 47%, and 73% reductions in cellulase activity, respectively. The Michaelis constant ( K m ) increased but the maximum catalytic velocity ( V max ) decreased for soil cellulase as a result of cultivation in the study areas. The thermodynamic parameters ( E a and Q 10 ) of soil cellulase were also affected by cultivation. Higher E a and Q 10 values were obtained for the native soils, but the lower values were observed in the cultivated soils. The cellulase zymographic pattern revealed different cellulase isoenzymes in the soils. The results confirm the hypothesis that differences in the kinetic and thermodynamic parameters of soil enzymes could be due to the presence of different isoenzymes. Key Words Cellulase, land use change, protein diversity, isoenzyme, kinetic and thermodynamic parameters, fungal diversity
