Аннотация:The radiothermometry (RTM) study of a cytochrome-containing system (CYP102 A1) has been conducted in order to demonstrate the applicability of RTM for monitoring changes in the functional activity of an enzyme in case of its point mutation. The study has been performed with the example of the wild-type cytochrome (WT) and its mutant type A264K. CYP102 A1 is a nanoscale protein-enzymatic system of about 10 nm in size. RTM uses a radio detector and can record the corresponding brightness temperature (Tbr) of the nanoscale enzyme solution within the 3.4–4.2 GHzfrequency range during enzyme functioning. It was found that the enzymatic reaction during thelauric acid hydroxylation at the wild-type CYP102 A1 (WT) concentration of ~109 Mis accompaniedby Tbr fluctuations of ~0.5–1 C. At the same time, no Tbr fluctuations are observed for the mutated forms of the enzyme CYP102 A1 (A264K), where one amino acid was replaced. We know that the activity of CYP102 A1 (WT) is ~4 orders of magnitude higher than that of CYP102 A1 (A264K).Wetherefore concluded that the disappearance of the fluctuation of Tbr CYP102 A1 (A264K) is associatedwith a decrease in the activity of the enzyme. This effect can be used to develop new methods fortesting the activity of the enzyme that do not require additional labels and expensive equipment, in comparison with calorimetry and spectral methods. The RTM is beginning to find application in the diagnosis of oncological diseases and for the analysis of biochemical processes