Phosphomonoesteras are a sub) and ADA (pH=6.5) buffers as alternatives for MUB buffer for the assays of alkaline and acid phosphomonoesterases, respectively. For these purposes six soil samples were collected from Isfahan and Chaharmahal-va-Bakhtiari provinces. For the first research, the soils of oak natural forest and its deforested counterpart were separated to different size classes including 2, 2-1, 1-0.5, 0.5-0.25, 0.25-0.05 mm either by wet or dry sieving procedures. Each aggregate size classes were analyzed for aggregate mass fraction, aggregate organic C content and alkaline and acid phosphomonoesterases. Relative contributions of the classes were calculated for the soil C content. The activities of the enzymes were measured per gram of soil aggregates and the relative contributions of size classes as well as their activity fractions were calculated. In the second research, the required pH, for the enzymes were provided by alternative buffers. The results of the first research revealed that deforestation has increased the fraction of the smaller soil aggregates so that the contribution of the large macroaggregated decreased from 30 to 10 percent. The shift was not equal for the two sieving procedure. The organic C content decreased as the aggregate sizes decreased. For any size class, soil organic C content was greater in the natural forest compared to the deforested counterpart. The distribution pattern of organic C in the aggregates was similar in the two sieving procedures. The distribution pattern of soil alkaline phosphatase among soil aggregate classes was affected by land use change. In the natural forest, the enzyme activity was decreased as the aggragate size decreased while; it was not the case for the deforested counterpart. No significant difference was observed among the aggregate size classes in the deforested counterpart. Similar patterns were observed for the relative contribution of the aggregates and their activity fractions. Acid phosphomonoesterase activity was also affected by land use change. In the natural forest, the activity of the enzyme decreased as the aggregate size decfreased. The trend could not be observed in the deforested counterpart. The relative countribution of the aggregates in the soil acid phosphomonoesterase as well as relative activity fraction followed similar pattern. The association among the soil organic C and the soil enzyme activities were positive in the natural forest and negative in the deforested counterpart. Results of the second research indicated that significant differences were obtained between classic versus proposed procedures for the assay of the phosphomonoesterases. Therefore, the TEA and ADA buffers cannot be used directly for their assays. However, significant correlation was observed between the classic and proposed procedures. Overall, using TEA and ADA could only measure 30 and 10 percent of their activities obtained by classic methods, respectively. Keywords phosphomonoesterases, enzyme aggregate distribution, aggregate relative contribution, activity fraction, TEA and ADA buffer