The aim of the study was to investigate the activity of purine nucleotide catabolism enzymes, in particular, AMP-deaminase, 5'-nucleotidase, guanosine deaminase, and guanosine phosphorylase and xanthine oxidase in the cytosolic fraction of the liver of rats under conditions of different dietary supply of sucrose and dietary proteins. Enzyme activity was determined by photo colorimetric method: AMP-deaminase activity by the amount of ammonia formed by deamination of AMP, which has a maximum absorption at λ-540 nm and 5'-nucleotidase activity by the amount of Pn formed by hydrolysis of AMP at λ-8. The activity of guanosine phosphorylase, guanosine deaminase and xanthine oxidase was determined by spectrophotometric method. The results of studies have shown that due to consuming a high-sucrose diet in on the background of protein deficiency, the activation of purine nucleotide catabolism is observed and it can lead to disruption of the regulation of energy-dependent processes in liver cells. A critical factor influencing on the state of the purine nucleotide system and the activity of enzymes of their catabolism is alimentary protein deficiency.