The 26S proteasome is a multi-subunit protein complex that consists of the catalytic 20S and regulatory 19S sub-complexes. The most well studied function of proteasomes is specific degradation of proteins. There are several purification schemes for obtaining the preparations of 26S proteasomes. An important step in purification of 26S proteasomes is concentration of the purified material for subsequent analysis of its biochemical functions. In this report we showed that the subunits composition of 26S proteasomes that have been concentrated by the different modes at the latest stage of their preparation is identical. However, the concentrating mode differently affects the functional activity of these complexes.