scholarly journals On the mechanism of the increase in cardiolipin biosynthesis and resynthesis in hepatocytes during rat liver regeneration

2005 ◽  
Vol 386 (1) ◽  
pp. 137-143 ◽  
Author(s):  
Jennifer WEBSTER ◽  
Jenny Y. JIANG ◽  
Biao LU ◽  
Fred Y. XU ◽  
William A. TAYLOR ◽  
...  
Keyword(s):  
Linoleic Acid ◽  
Liver Regeneration ◽  
Rat Liver ◽  
De Novo ◽  
Fold Increase ◽  
Enzymic Activity ◽  
Pool Size ◽  
De Novo Biosynthesis ◽  
Key Enzyme ◽  
Rate Limiting

CL (cardiolipin) is a major mitochondrial membrane phospholipid important for the regulation of mitochondrial function. We examined CL de novo biosynthesis and its resynthesis in isolated rat liver hepatocytes prepared 48 h subsequent to two-thirds PHx (partial hepatectomy). The pool size of CL and its de novo biosynthesis from [1,3-3H]glycerol were increased 3.3-fold (P<0.05) and 3.1-fold (P<0.05) respectively in hepatocytes prepared from PHx rats compared with sham-operated controls. The reason for the increased CL biosynthesis was a 65% increase (P<0.05) in enzymic activity in PGP-S (phosphatidylglycerolphosphate synthase), a key enzyme in de novo CL biosynthesis. The increase in PGP-S activity was due to a 3-fold increase (P<0.05) of hepatic PGP-S mRNA expression. The increase in de novo CL biosynthesis and pool size corresponded to a 2.3-fold increase (P<0.05) in the amount of [1-14C]linoleic acid incorporated into CL of hepatocytes prepared from PHx rats compared with sham-operated controls, indicating an increase in CL resynthesis. The activity of MLCL-AT (monolysocardiolipin acyltransferase), a rate-limiting enzyme of CL resynthesis, was increased by 43% (P<0.05) in hepatocytes prepared from PHx rats compared with sham-operated controls; this result would explain the increase in [1-14C]linoleic acid incorporation into CL. The increase in MLCL-AT activity was due to an increase in hepatic MLCL-AT protein expression. The results show that CL de novo biosynthesis and its resynthesis are increased during liver regeneration.

scholarly journals De novo biosynthesis of linoleic acid is widespread in parasitic wasps

2021 ◽  
Author(s):  
Bastian Broschwitz ◽  
Lorena Prager ◽  
Tamara Pokorny ◽  
Joachim Ruther
Keyword(s):  
Linoleic Acid ◽  
De Novo ◽  
Parasitic Wasps ◽  
De Novo Biosynthesis

Regulation of the purine salvage pathway in rat liver

1992 ◽  
Vol 262 (3) ◽  
pp. E344-E352 ◽  
Author(s):  
Y. A. Kim ◽  
M. T. King ◽  
W. E. Teague ◽  
G. A. Rufo ◽  
R. L. Veech ◽  
...  
Keyword(s):  
Rat Liver ◽  
De Novo ◽  
Equilibrium Constants ◽  
Purine Metabolism ◽  
Purine Salvage ◽  
Rate Limiting Step ◽  
Delta G ◽  
Salvage Pathways ◽  
Rate Limiting

The regulation of purine metabolism in rat liver has been examined under conditions that alter the flux through the pathway. Rats were given intraperitoneal injections of ethanol, sodium acetate, or sodium phosphate to attain body water concentrations of approximately 70, 20, and 10 mM, respectively. The livers were freeze-clamped after 30 min, and extracts were made for the analysis of metabolites, cofactors, purine bases, and nucleosides; homogenates were made for the measurement of the activities and kinetic parameters of seven enzymes that participate in purine salvage. The values of the equilibrium constants of nine reactions were determined in vitro and compared with the ratios of the reactants measured in liver. The changes in phosphoribosylpyrophosphate (PRPP), a key intermediate in both the de novo and salvage pathways of purine metabolism, were directly correlated with the changes in ribose 5-phosphate (ribose-5-P); ([PRPP] = 1.7[ribose-5-P] - 7.4 mumol/kg). Ribose-5-P concentrations in turn could be predicted from the liver content of fructose 6-phosphate and glyceraldehyde 3-phosphate by calculation from the known equilibria. The maximum velocities in the tissue of the seven enzymes measured were calculated from the measured substrate values in the liver and with consideration of other effectors of enzyme activity. PRPP synthetase was the least active of the enzymes measured, indicating a possible rate-limiting step. The delta G of the enzyme steps differed from equilibrium values by factors ranging from 4 (nucleoside phosphorylase) to 10(5) (PRPP synthetase and purine transferase reactions). The regulation of purine salvage appeared to depend on the levels of PRPP and ribose-5-P.

Increased rate of purine biosynthesis in rat liver after bilateral adrenalectomy

1986 ◽  
Vol 251 (4) ◽  
pp. E373-E378
Author(s):  
M. Itakura ◽  
N. Maeda ◽  
K. Yamashita
Keyword(s):  
Rat Liver ◽  
Turnover Rate ◽  
De Novo ◽  
Specific Activity ◽  
Pool Size ◽  
Purine Biosynthesis ◽  
Purine Synthesis ◽  
Metabolic Pool ◽  
Inhibitory Potential ◽  
Size Data

In bilaterally adrenalectomized rat liver the increased rate of de novo purine synthesis was shown by the increased [14C]glycine incorporation into hepatic acid-soluble purines with unchanged rapidly miscible glycine pool size and its turnover rate and by the increased rate of chasing of radiolabeled purines. At 24 h after adrenalectomy, the rate of de novo purine synthesis increased by 70%, 5-phosphoribosyl-1-pyrophosphate (PRPP) content increased by 200%, the specific activity of amidophosphoribosyltransferase (EC 2.4.2. 14; ATase) did not change, ATP and GTP showed a 33 and 24% decrease, and AMP and ADP showed a 245 and 38% increase. Combined, the metabolic pool size data reflected an unchanged total inhibitory potential on ATase. Replacement with corticosterone acetate for 24 h partially restored some of these abnormalities. These results suggest that the increase in the rate of de novo purine synthesis in adrenalectomized rat liver is secondary to increased catabolism of purine ribonucleotides and mediated by increased PRPP concentrations.

De novo biosynthesis of linoleic acid in insects

1986 ◽  
Vol 876 (3) ◽  
pp. 572-580 ◽  
Author(s):  
Colleen Cripps ◽  
Gary J. Blomquist ◽  
Mertxe de Renobales
Keyword(s):  
Linoleic Acid ◽  
De Novo ◽  
De Novo Biosynthesis

scholarly journals Age-associated perturbations in glutathione synthesis in mouse liver

2007 ◽  
Vol 405 (3) ◽  
pp. 583-589 ◽  
Author(s):  
Dikran Toroser ◽  
Rajindar S. Sohal
Keyword(s):  
Mouse Liver ◽  
De Novo ◽  
Catalytic Efficiency ◽  
Fold Increase ◽  
Age Related ◽  
Tissue Homogenates ◽  
Synthetic Capacity ◽  
Rate Limiting ◽  
Old Mice ◽  
Young Mice

The nature of the mechanisms underlying the age-related decline in glutathione (GSH) synthetic capacity is at present unclear. Steady-state kinetic parameters of mouse liver GCL (glutamate–cysteine ligase), the rate-limiting enzyme in GSH synthesis, and levels of hepatic GSH synthesis precursors from the trans-sulfuration pathway, such as homocysteine, cystathionine and cysteine, were compared between young and old C57BL/6 mice (6- and 24-month-old respectively). There were no agerelated differences in GCL Vmax, but the apparent Km for its substrates, cysteine and glutamate, was higher in the old mice compared with the young mice (∼800 compared with ∼300 μM, and ∼710 compared with 450 μM, P<0.05 for cysteine and glutamate in young and old mice respectively). Amounts of cysteine, cystathionine and Cys-Gly increased with age by 91, 24 and 28% respectively. Glutathione (GSH) levels remained unchanged with age, whereas GSSG content showed an 84% increase, suggesting a significant pro-oxidizing shift in the 2GSH/GSSG ratio. The amount of the toxic trans-sulfuration/glutathione biosynthetic pathway intermediate, homocysteine, was 154% higher (P<0.005) in the liver of old mice compared with young mice. The conversion of homocysteine into cystathionine, a rate-limiting step in trans-sulfuration catalysed by cystathionine β-synthase, was comparatively less efficient in the old mice, as indicated by cystathionine/homocysteine ratios. Incubation of tissue homogenates with physiological concentrations of homocysteine caused an up to 4.4-fold increase in the apparent Km of GCL for its glutamate substrate, but had no effect on Vmax. The results suggest that perturbation of the catalytic efficiency of GCL and accumulation of homocysteine from the trans-sulfuration pathway may adversely affect de novo GSH synthesis during aging.

scholarly journals IMPDH2: a new gene associated with dominant juvenile-onset dystonia-tremor disorder

2021 ◽  
Author(s):  
Anna Kuukasjärvi ◽  
Juan C. Landoni ◽  
Jyrki Kaukonen ◽  
Mika Juhakoski ◽  
Mari Auranen ◽  
...  
Keyword(s):  
De Novo ◽  
Inosine Monophosphate Dehydrogenase ◽  
Juvenile Onset ◽  
De Novo Biosynthesis ◽  
Whole Exome ◽  
Dopamine Biosynthesis ◽  
Dehydrogenase Gene ◽  
New Gene ◽  
Rate Limiting ◽  
Generation Sequencing

AbstractThe aetiology of dystonia disorders is complex, and next-generation sequencing has become a useful tool in elucidating the variable genetic background of these diseases. Here we report a deleterious heterozygous truncating variant in the inosine monophosphate dehydrogenase gene (IMPDH2) by whole-exome sequencing, co-segregating with a dominantly inherited dystonia-tremor disease in a large Finnish family. We show that the defect results in degradation of the gene product, causing IMPDH2 deficiency in patient cells. IMPDH2 is the first and rate-limiting enzyme in the de novo biosynthesis of guanine nucleotides, a dopamine synthetic pathway previously linked to childhood or adolescence-onset dystonia disorders. We report IMPDH2 as a new gene to the dystonia disease entity. The evidence underlines the important link between guanine metabolism, dopamine biosynthesis and dystonia.

Increased rate of de novo purine synthesis and its mechanism in regenerating rat liver

1986 ◽  
Vol 251 (5) ◽  
pp. G585-G590 ◽  
Author(s):  
M. Itakura ◽  
N. Maeda ◽  
M. Tsuchiya ◽  
K. Yamashita
Keyword(s):  
Rat Liver ◽  
Turnover Rate ◽  
De Novo ◽  
Pool Size ◽  
Purine Synthesis ◽  
Regenerating Rat Liver ◽  
The Mean

In regenerating rat liver at 12 h after a 70% hepatectomy, [14C]glycine incorporation to hepatic acid-soluble purines increased by 2.4-fold with a 26% increase of the mean rapidly miscible glycine pool size and its comparable turnover rate. Amidophosphoribosyltransferase (EC 2.4.2.14, ATase) activity increased 1.8-fold at 18 h and 5-phosphoribosyl-1-pyrophosphate (PRPP) concentration increased 3.0-fold at 12 h after surgery. Decreases in ATP and GTP concentrations of 13 and 15%, respectively, in regenerating rat liver at 12 h after surgery were counterbalanced by increased AMP and GMP concentrations of 13 and 44%, respectively, with comparable inhibitory potentials on ATase. These results suggest than an increased rate of de novo purine synthesis in regenerating rat liver is mediated by the increased ATase activity and PRPP concentrations.

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