Abstract. We carried out testing of the enzyme activity level (catalase, invertase, polyphenol oxidase) in natural and anthropogenically converted soils of Rostov-on-Don's (Russia) suburban, park, residential and industrial zones. The soil enzyme activity under conditions of urban pedogenesis is significantly lower (2 or 3 times) than in out-of-town analogs. Duration of soil sealing considerably influences biological activity, and, the longer this period the higher the negative impact on activity of researched enzyme is. Nevertheless, there is a close connection between soil humus condition and its enzyme activity: the activity of the above mentioned enzyme is highest in horizons containing the largest number of organic substance
