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Biomedical subjects

G L Tritsch

Publications and source records attributed to G L Tritsch.

At least 55 records · Page 3Linked to original sources
PubMed1976

Adenosine aminohydrolase from monkey brain: partial purification and some kinetic properties.

Adenosine aminohydrolase from monkey brain was purified ten fold. In pH 7.3 phosphate buffer at 37 degrees, this enzyme preparation deaminated adenosine and arabinosyladenine with apparent values for the Michaelis constant of 32 muM and 370 muM respectively. The products of both deamination reactions, i.e., inosine and arabinosylhypoxanthine, were competitive inhibitors with Ki equal to 220 muM and 1,000 muM, respectively. N6-benzyladenosine and 9-(1-hydroxy-2-octyl)adenine were competitive inhibitors and were more effective in inhibiting deamination of arabinosyladenine than of adenosine. It is suggested that these compounds might potentiate arabinosyladenine chemotherapy of neoplasms of the central nervous system.

Adenosine Deaminase↗
PubMed1975

Purine and pyrimidine inhibitors of arginase.

1. Adenosine, inosine, adenine and uric acid are competitive inhibitors and cytidine and cytosine noncompetitive inhibitors of bovine liver arginase (L-arginine amidinohydrolase, EC 3.5.3.1). 2. The affinity of the enzyme for these inhibitors was 10--100 times as great as for substrate in terms of Ki versus Km. 3. These nucleic acid metabolites may thus function in vivo to regulate the urea cycle. 4. Several naturally occuring competitive and noncompetitive inhibitors of arginase of unknown structure have been isolated from plant and animal tissue. From their properties and methods of isolation, they may be the purines and pyrimidines herein described. 5. These purines and pyrimidines have no effect on tryptic hydrolysis.

Animals↗
PubMed1975

Clinical and experimental studies on adenine, various nucleosides and their analogs in hematology.

In red blood cells as well as in platelets there appears to be a decrease in adenine nucleotides during storage under blood bank conditions. This can be decreased by use of anticoagulant preservatives with higher phosphate content than the standard ACD solution, through the addition of adenine and inosine. Maintenance of higher ATP levels appears to be related to longer circulating life span after transfusion into patients in the case of red blood cells but not platelets. Inosine and more alkaline preservative medium also contribute to the maintenance of 2,3-DPG levels in red blood cells, and with it to the maintenance of normal hemoglobin dissociation curves and thus oxygen-carrying capacity. Certain nucleoside analogs may contribute to the preservation of platelets and of whole blood by their platelet-aggregation inhibitory activity. Platelet-aggregation inhibitors may also be useful in preventing thromboembolic episodes with potentially greater safety than anticoagulants.

Adenine↗
PubMed1975

Synthesis and antitumor activity of 5'-phosphates and cyclic 3',5'-phosphates derived from biologically active nucleosides.

Syntheses and biological activities of 12 N6-substituted adenosine 5'-phosphates and 15 cyclic 3',5'-phosphates are described. Included among these are the cyclic phosphates of the naturally occurring anticodon adjacent modified nucleosides, N6-(delta2-isopentenyl)adenosine and N-(purin-6-ylcarbamoyl)-L-threonine ribonucleoside. Also reported in this paper are the 5'-phosphates and cyclic phosphates of the cytokinins, N6-benzyladenosine, kinetin ribonucleoside, 3-(chloro-trans-2-buten-2-yl)adenosine,6-o-chlorophenylureidopurine ribonucleoside, and 6-allylureidopurine ribonucleoside. The 5'-nucleotides were prepared by direct phosphorylation of the corresponding ribonucleosides with POCl3 and triethyl phosphate. These compounds were converted to the cyclic 3',5'-phosphates by cyclization of the corresponding 5'-nucleotides with dicyclohexylcarbodiimide. Comparison of the cytotoxicity of the ribonucleosides with their 5'-nucleotides and cyclic 3',5'-nucleotides showed that some of the 5'-phosphates and cyclic phosphates were almost as active as the parent nucleosides. The 5'-nucleotides and the cyclic phosphates were more soluble than the parent nucleosides. The cyclic 3',5'-nucleotides were examined as alternate activators of cAMP-dependent protein kinase from beef heart. While all of the analogs studied showed some activity toward this enzyme, several compounds were more effective than cAMP itself. The analogs were also tested as substrates for cyclic 3',5'-nucleotide phosphodiesterase from beef heart. The N6-alkyl-cAMP analogs were poor substrates for the enzyme, while N6-carbamoyl-cAMP derivatives were inert toward this enzyme. These compounds did not inhibit the phosphodiesterase. Some of the cyclic phosphates exhibited marginal effect in the inhibition of glycogen synthesis in skin slices.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1975

Synthesis and biological activities of some N6-(nitro- and -aminobenzyl)adenosines.

Synthesis and biological activities of 12 analogs of N6-benzyladenosine are described. The compounds were prepared by two methods: (1) direct alkylation of adenosine with an appropriately substituted benzyl bromide to give the N1-substituted derivative which was then rearranged in base to give the N6-substituted compound, and (2) by nucleophilic displacement of chlorine in 6-chloropurine ribonucleoside, 6-chloro-2-aminopurine ribonucleoside, and 6-chloro-2-aminopurine with an amine. These analogs were examined for their growth inhibitory effect in cultured leukemic cells and also for their effect on adenosine aminohydrolase activity. N6-p-Nitrobenzyladenosine and its 2'-deoxy analog were competitive inhibitors (K1 65, 22 MUM). The 2-amino-N6-p-nitrobenzyladenine and its ribonucleoside were found to be noncompetitive inhibitors of adenosine aminohydrolase. In cultured L1210 leukemia, 2-amino-6-p-nitrobenzylaminopurine and the corresponding ribonucleoside were better growth inhibitors than N6-benzyladenosine, while N6-p-nitrobenzyladenosine, its 2'-deoxy analog, and N6-p-fluorobenzyladenosine were as active as N6-benzyladenosine.

Adenosine↗
PubMed1975

Effect of N6-(delta2-isopentenyl)adenosine treatment in vivo on hexokinase activity of mouse L 1210 cells.

The kinetic properties of hexokinase of L1210 ascites tumor cells propagated in DBA/2HaD mice are altered by treatment of the mice with the modified nucleoside N6-(delta2-isopentenyl)-adensone (IPA). Relative to animals not treated with IPA, ascites cell hexokinase showed an increased affinity for ATP and a decreased affinity for glucose as a result of IPA treatment. The heat stability of the enzyme was different in treated and untreated mice. It was concluded that IPA treatment may either produce changes in enzyme conformation which resulted in a change in control mechanisms or may induce the formation of a hexokinase isoenzyme.

Adenosine↗