It is difficult, however, to establish whether low enzymatic activity occur because of metal inhibition, or from low concentrations of the enzyme resulting from impeded microbial growth and enzyme synthesis (Tyler, 1974). The metal susceptibility of enzyme activities was reported by Kandeler et al. (1996), Kuperman and Carreiro (1997) and Kunito et al. (2001). The inhibition of enzyme activities by metals in soils is principally attributed to an indirect effect (suppression of microbial population and cellular activities) and/or a direct effect (inactivation of extracellular enzymes due to binding with metals).