[Effect of adenosine on synthesis of pyrimidine nucleotides and RNA in normal lymphocytes and under conditions of chronic lymphoid leukosis]. / Vliianie adenozina na sintez pirimidinovykh nukleotidov i RNK v normal'nykh limfots takh i pri khronicheskom limfoleikoze.

Effect of exogenous adenosine on synthesis of pyrimidine nucleotides and RNA was studied in lymphocytes of the patients with leukemic form of chronic lymphoid leukosis. In presence of adenosine lymphocytes were incubated in mixtures containing the precursors--2,3-2(3)H-aspartic and 2-14C-orotic acids as well as 5-3H-uridine. Effect of adenosine on the activity of key enzymes of pyrimidine nucleotide synthesis (orotidine monophosphate pyrophosphorylase and uridine kinase) was studied. The enzymatic activity was estimated using radiochemical procedures in extracts of lymphocytes stored at -20 degrees after acetone drying. Adenosine similarly inhibited synthesis of pyrimidine nucleotides and RNA in normal and leukemic leukocytes. One of the mechanisms, by means of which the inhibitory effect of adenosine was realized, was related to the enzymatic activity of orotidine monophosphate pyrophosphorylase and uridine kinase.

[Coordination of the main and reutilization pathways of nucleotide biosynthesis in the lymphocytes in leukemia]. / Koordinatsiia osnovnogo i reutilizatsionnogo putei biosinteza nukleotidov v limfotsitakh pri leikoze.

Coordination of these two pathways of nucleotide synthesis in leukocytes under chronic lympholeukosis was studied using incorporation of 14C-orotic acid and 14C-uridine into uridine mono-, di- and triphosphates and also into RNA. Simultaneously, activity of the key enzymes, participating in metabolism of orotic acid and of uridine, was measured: OMP-pyrophosphorylase /EC 2.4.2.10, orotidine-5'-phosphate: purophosphate phosphorybosyl transferase/ and uridine kinase /EC 2.7.1.48, ATP: uridine-5'-phosphotransferase/. The reutilizational pathway of pyrimidine nucleotide synthesis was distinctly activated. At the same time there was only a slight increase in the main pathway of their synthesis in lymphocytes in leukemic form of cronic lympholeukosis. Activities of OMP-pyrophosphorylase and uridine kinase were increased by 30%. An impairment in the coordination of the rates of both pathways of pyrimidine nucleotide synthesis was related to inhibition of OMP-pyrophosphorylase caused by and increase in uridine nucleotide pool.

[Alteration of leukocyte AMP- and IMP-pyrophosphorylase stability in leukemia]. / Izmenenie termostabil'nosti AMF- i IMF-pirofosforilazy leikotsitov pri leikozakh.

Effect of thermic treatment and of pre-incubation with phosphoribosyl pyrophosphate on activity of AMP- and IMP-pyrophosphorylases were studied in leukocytes under chronic forms of limpho- and myeloleukoses. AMP-pyrophosphorylase from leukemia leukocytes was inactivated after heating up to 65 degrees, which, at the same time, as distinct from the enzyme of normal leukocytes, proved to be reversibly reduced after incubation of the heated cell extracts with phosphoribosyl pyrophosphate. IMP-pyrophosphorylase of leukocytes was activated at this temperature; the activation of the enzyme was 15--20% higher in leukemic leukocytes than in leukocytes of healthy donors. The data obtained demonstrate the increased thermostability of purine nucleotide pyrophosphorylase from leukemic leukocytes, which is apparently due to conformational peculiarities of the enzyme molecules.

[Phosphoribosyl pyrophosphate and its metabolic enzymes in the erythrocytes in certain forms of anemia]. / Fosforibozilpirofosfat i fermenty ego obmena v éritrotsitakh pri nekotorykh formakh anemii

Content of phosphoribosyl pyrophosphate and the activity of ribose phosphate pyrophosphokinase and AMP-pyrophosphorylase were studied in erythrocytes of healthy persons and of patients with various types of anemia. Deficiency of phosphoribosyl pyrophosphate and a decrease in the activity of enzymes studied were observed in erythrocytes under microspherocytic and hypoplastic anemia. The alterations correlated with impairments in energy metabolism. At the same time an activation of phosphoribosyl pyrophosphate enzymatic system and an increase of its content in erythrocytes did not depend on energy metabolism in Marchiafava--Micheli disease.

[A modified method for phosphoribosyl pyrophosphate synthesis]. / Modifitsirovannyi metod sinteza fosforibozilpirofosfata

A modified method for synthesis of phosphoribosyl pyrophosphate (PRPP) from ribose-5-phosphate and ATP in presence of ribose phosphate pyrophosphokinase (RPPPK) was developed. RPPPK was isolated from extracts of acetone powder of rabbit liver tissue, using alcohol fractionation of proteins. The protein fraction, containing RPPPK, was isolated at 35% saturation with 96% ethyl alcohol. The identification of the synthesized preparation of PRPP was carried out in enzymatic reaction with adenine- and inosine phosphoribosyl transferases, using labelled adenine and guanine. The obtained product of reaction (AMP and GMP) were precipitated with lantane chloride.