Metabolism of purine nucleosides and phosphoribosylpyrophosphate in thymocytes and splenocytes of various mammalian species.

This research investigates the differing activities of specific enzymes in thymocytes and splenocytes in various mammals, including newborn humans, horses, pigs, sheep, rats, and mice. It emphasizes on the distinctions between enzyme activities when considering cells count versus protein content and how these activities relate to the metabolism of purine nucleosides and phosphoribosylpyrophosphate.

Enzymes Activity in Different Mammals and Cell Types

• The researchers measured the activity of three enzymes: Adenosine deaminase (ADA), Purine nucleoside phosphorylase (PNP), and Adenylate Kinase (AK) in two types of immune cells: thymocytes and splenocytes. These cells were taken from newborn humans, as well as young animals of different species including horses, pigs, sheep, rats, and mice.
• The results showed that the activity of ADA was generally higher in thymocytes than in lymphocytes for every species except horses. The highest ADA activity was found in pig and sheep splenocytes, while the lowest in horse lymphoid cells.
• PNP activity showed the opposite tendency to ADA: it was lower in thymocytes than in lymphocytes, except for horses. Human lymphocytes showed the highest PNP activity, and ovine (sheep) thymocytes the lowest.

Activity of Other Enzymes

• They also measured the activity of Adenylate Kinase (AK), which was found to be similar in thymocytes of all species studied, and consistently lower than ADA activity. However, in human, horse, and pig splenocytes, AK activity was found to be comparable to that in thymocytes.
• The activity of a different enzyme, deoxyguanosine kinase, was found to be at its lowest in rat thymocytes, but highest in humans.
• The researchers noted that when the enzyme activities were represented in relation to total protein content (per milligram of protein) instead of cell numbers (per 10(6) cells), the differences between thymocytes and lymphocytes became less pronounced.

Activity of PRPP synthetase and Concentration of PRPP

• The research also analyzed the activity of phosphoribosyl pyrophosphate (PRPP) synthetase. The activity of this enzyme was similar in thymocytes, splenocytes, and lymphocytes of the same species, and also between different species.
• The concentration of PRPP itself was found to be lowest in sheep thymocytes, and generally higher in splenocytes than in thymocytes of the same species, with humans as the exception.