scholarly journals Enzymes of the pathway of purine synthesis in the rat mammary gland. Changes in the lactation cycle and the effects of diabetes

1988 ◽  
Vol 250 (2) ◽  
pp. 395-399 ◽  
Author(s):  
S Beardsley ◽  
S Kunjara ◽  
A L Greenbaum
Keyword(s):  
Mammary Gland ◽  
De Novo ◽  
Salvage Pathway ◽  
Adenine Phosphoribosyltransferase ◽  
Phosphoribosyl Pyrophosphate ◽  
Purine Synthesis ◽  
Enzyme Change ◽  
Rat Mammary Gland ◽  
Salvage Pathways ◽  
Lactation Cycle

Measurements were made of the activities of the enzymes of the ‘de novo’ and salvage pathways of purine synthesis [phosphoribosyl pyrophosphate amidotransferase (EC 2.4.2.14), adenine phosphoribosyltransferase (EC 2.4.2.7) and hypoxanthine phosphoribosyltranferase (EC 2.4.2.8)] at different stages of the lactation cycle, and the effects of diabetes on the activity of these enzymes in lactation were studied. A distinctive pattern of enzyme change was observed, in which the ‘de novo’ pathway enzyme phosphoribosyl pyrophosphate amidotransferase increased sharply between days 10 and 14 of pregnancy, and then remained sensibly constant until the height of lactation, whereas the enzymes of the salvage pathway increased later in pregnancy and continued to rise during lactation. Diabetes severely depressed the activity of the enzymes of the salvage pathway, but appeared to be without effect on the ‘de novo’ pathway enzyme. These results are discussed in relation to the provision of purine precursors from tissues outside the mammary gland.

scholarly journals Phosphoribosyl pyrophosphate and phosphoribosyl pyrophosphate synthetase in rat mammary gland. Changes in the lactation cycle and effects of diabetes, insulin and phenazine methosulphate

1986 ◽  
Vol 238 (2) ◽  
pp. 553-559 ◽  
Author(s):  
S Kunjara ◽  
M Sochor ◽  
N Salih ◽  
P McLean ◽  
A L Greenbaum
Keyword(s):  
Mammary Gland ◽  
Fold Increase ◽  
Pentose Phosphate ◽  
Diabetic Rat ◽  
Synthetase Activity ◽  
Phosphoribosyl Pyrophosphate ◽  
Rat Mammary Gland ◽  
Lactation Cycle ◽  
Phenazine Methosulphate

Changes in the tissue content of phosphoribosyl pyrophosphate (PPRibP), glucose 6-phosphate, ribose 5-phosphate (Rib5P), RNA and DNA, of the activity of PPRibP synthetase (EC 2.7.6.1) and the conversion of [1-14C]- and [6-14C]-glucose into 14CO2 were measured at mid-lactation in the normal and diabetic rat and in pregnancy, lactation and mammary involution in the normal rat. The PPRibP, glucose 6-phosphate and Rib5P contents increase during pregnancy and early lactation to reach a plateau value at mid-lactation, before falling sharply during weaning. The PPRibP content, PPRibP synthetase activity and flux of glucose through the oxidative pentose phosphate pathway (PPP) all change in parallel during the lactation cycle. Similarly, after 3 and 5 days duration of streptozotocin-induced diabetes, ending on day 10 of lactation, there were parallel declines in PPRibP content, PPRibP synthetase and PPP activity. The effect of streptozotocin was prevented by pretreatment with nicotinamide and partially reversed by insulin administration. Addition of insulin to lactating rat mammary-gland slices incubated in vitro significantly raised the PPRibP content (+47%) and the activity of the PPP (+40%); phenazine methosulphate, which gives a 2-fold increase in PPP activity, raised the PPRibP content of lactating mammary gland slices by approx. 3-fold. It is concluded that Rib5P, generated in the oxidative segment of the PPP, is an important determinant of PPRibP synthesis in the lactating rat mammary gland and that insulin plays a central role in the regulation of the bioavailability of this precursor of nucleotide and nucleic acid synthesis.

scholarly journals Renal hypertrophy in experimental diabetes. The activity of the ‘de novo’ and salvage pathways of purine [corrected] synthesis

1988 ◽  
Vol 249 (3) ◽  
pp. 911-914 ◽  
Author(s):  
S Kunjara ◽  
S J Beardsley ◽  
A L Greenbaum
Keyword(s):  
Nucleic Acids ◽  
De Novo ◽  
Experimental Diabetes ◽  
Salvage Pathway ◽  
Phosphoribosyl Pyrophosphate ◽  
Renal Hypertrophy ◽  
Early Diabetes ◽  
Nucleotide Synthesis ◽  
Main Route ◽  
Salvage Pathways

Measurements were made of the activity of phosphoribosyl pyrophosphate amidotransferase (PPRibP-At, EC 2.4.2.14) and of adenine (APRT, EC 2.4.2.7) and hypoxanthine (HPRT, EC 2.4.2.8) phosphoribosyltransferases, representing the ‘de novo’ and salvage pathways respectively. PPRibP-At activity increased within 3 days of diabetes, whereas APRT and HPRT increased later. Incorporation of [14C]formate and of [8-14C]adenine into the nucleic acids of kidney slices showed that formate was incorporated earlier, and to a greater extent, than was adenine. These results indicate that, although the ‘de novo’ pathway for nucleotide synthesis is the main route in early diabetes, the salvage pathway assumes greater importance at later stages.

scholarly journals Enzymic changes in rabbit and rat mammary gland during the lactation cycle

1969 ◽  
Vol 112 (3) ◽  
pp. 293-301 ◽  
Author(s):  
Bilquis Gul ◽  
R. Dils
Keyword(s):  
Mammary Gland ◽  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Acid Synthesis ◽  
Mitochondrial Fraction ◽  
Soluble Form ◽  
Supernatant Fraction ◽  
Rat Mammary Gland ◽  
Lactation Cycle

1. Activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), isocitrate dehydrogenase (EC 1.1.1.42), malate dehydrogenase (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (EC 1.1.1.40), and pyruvate carboxylase (EC 6.4.1.1) were determined in subcellular fractions of mammary gland from rabbits during pregnancy, at different stages of lactation and during weaning. The results were compared with those obtained in similar experiments with rat mammary gland. 2. Three bases of expression of the activity of enzymes in the particle-free supernatant fraction of mammary gland were compared. During lactation, activity expressed per mg. of particle-free supernatant protein (uncorrected for milk protein) correlated well with that expressed per μg. of DNA phosphorus. The disadvantages of expressing activities per g. wet wt. are discussed. 3. The major differences between the two tissues were: (a) neither malate dehydrogenase (decarboxylating) nor a soluble form of pyruvate carboxylase could be detected in rabbit mammary gland at any stage of the lactation cycle; (b) isocitrate dehydrogenase increased in activity during lactation in rabbit mammary gland, but not in that of the rat. 4. Pyruvate carboxylase in the mitochondrial fraction of rabbit mammary gland, and in both the mitochondrial and the soluble fractions of rat mammary gland, did not change in activity during lactation. 5. For each tissue, the NADP-dependent dehydrogenases studied had a high activity at all stages of the lactation cycle compared with the rate of fatty acid synthesis at mid-lactation. The significance of these results is discussed with respect to the supply of NADPH via NADH.

Pyrimidine nucleotide synthesis in the rat mammary gland: Changes in the lactation cycle and effects of diabetes

1992 ◽  
Vol 48 (3) ◽  
pp. 263-274 ◽  
Author(s):  
Sirilaksana Kunjara ◽  
Milena Sochor ◽  
Michael Bennett ◽  
A.Leslie Greenbaum ◽  
Patricia McLean
Keyword(s):  
Mammary Gland ◽  
Nucleotide Synthesis ◽  
Pyrimidine Nucleotide ◽  
Rat Mammary Gland ◽  
Lactation Cycle

Enzymes of the de novo and Salvage Pathways of Purine Synthesis in Renal Hypertrophy

Enzyme ◽  
1988 ◽  
Vol 40 (4) ◽  
pp. 231-237 ◽  
Author(s):  
Steven Beardsley ◽  
Sirilaksana Kunjara ◽  
Milena Sochor ◽  
Leslie Greenbaum
Keyword(s):  
De Novo ◽  
Renal Hypertrophy ◽  
Purine Synthesis ◽  
Salvage Pathways

scholarly journals Study of purinosome assembly in cell-based model systems with de novo purine synthesis and salvage pathway deficiencies

PLoS ONE ◽  
2018 ◽  
Vol 13 (7) ◽  
pp. e0201432 ◽  
Author(s):  
Veronika Baresova ◽  
Vaclava Skopova ◽  
Olga Souckova ◽  
Matyas Krijt ◽  
Stanislav Kmoch ◽  
...  
Keyword(s):  
De Novo ◽  
Model Systems ◽  
Salvage Pathway ◽  
Purine Synthesis

Cell cycle regulation of purine synthesis by phosphoribosyl pyrophosphate and inorganic phosphate

2013 ◽  
Vol 454 (1) ◽  
pp. 91-99 ◽  
Author(s):  
Alla Fridman ◽  
Arindam Saha ◽  
Adriano Chan ◽  
Darren E. Casteel ◽  
Renate B. Pilz ◽  
...  
Keyword(s):  
De Novo ◽  
Fold Increase ◽  
Pentose Phosphate ◽  
S Phase ◽  
G1 Phase ◽  
Synthetase Activity ◽  
Phosphoribosyl Pyrophosphate ◽  
Purine Synthesis ◽  
Oxidative Pathway ◽  
Intracellular Phosphate

Cells must increase synthesis of purine nucleotides/deoxynucleotides before or during S-phase. We found that rates of purine synthesis via the de novo and salvage pathways increased 5.0- and 3.3-fold respectively, as cells progressed from mid-G1-phase to early S-phase. The increased purine synthesis could be attributed to a 3.2-fold increase in intracellular PRPP (5-phosphoribosyl-α-1-pyrophosphate), a rate-limiting substrate for de novo and salvage purine synthesis. PRPP can be produced by the oxidative and non-oxidative pentose phosphate pathways, and we found a 3.1-fold increase in flow through the non-oxidative pathway, with no change in oxidative pathway activity. Non-oxidative pentose phosphate pathway enzymes showed no change in activity, but PRPP synthetase is regulated by phosphate, and we found that phosphate uptake and total intracellular phosphate concentration increased significantly between mid-G1-phase and early S-phase. Over the same time period, PRPP synthetase activity increased 2.5-fold when assayed in the absence of added phosphate, making enzyme activity dependent on cellular phosphate at the time of extraction. We conclude that purine synthesis increases as cells progress from G1- to S-phase, and that the increase is from heightened PRPP synthetase activity due to increased intracellular phosphate.

Guanosine metabolism in Neurospora crassa

1980 ◽  
Vol 58 (5) ◽  
pp. 369-376 ◽  
Author(s):  
W. L. Greer ◽  
L. Pendyala ◽  
A. M. Wellman
Keyword(s):  
Neurospora Crassa ◽  
Biosynthetic Pathway ◽  
De Novo ◽  
Nutritional Supplement ◽  
Inhibitory Effect ◽  
Hypoxanthine Phosphoribosyltransferase ◽  
Wild Type ◽  
Adenine Phosphoribosyltransferase ◽  
Purine Synthesis ◽  
De Novo Biosynthesis

Two aspects of guanosine metabolism in Neurospora have been investigated, (a) The inability of adenine mutants (blocked prior to IMP synthesis) to use guanosine as a nutritional supplement; and (b) the inhibitory effect of guanosine on the utilization of hypoxanthine as a purine source for growth by these mutants. Studies on the utilization of guanosine indicated that the proportion of adenine derived from guanosine may be limiting for the growth of adenine mutants. In wild type, adenine is produced through the biosynthetic pathway when grown in the presence of guanosine The amount of adenine produced through the de novo biosynthesis in wild type increases with increasing concentrations of guanosine in the medium. However, the total purine synthesis does not increase. Guanosine inhibits the uptake of hypoxanthine severely. In addition, guanosine and its nucleotide derivatives also inhibit the hypoxanthine phosphoribosyltransferase activity, at the same time stimulating the adenine phosphoribosyltransferase activity. Guanosine's effects on the uptake of hypoxanthine and its conversion to the nucleotide form may be the reasons why guanosine inhibits the utilization of hypoxanthine but not adenine by these mutants.

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