Ammonia production in muscle and other tissues: the purine nucleotide cycle.

1972 ◽  
Vol 52 (2) ◽  
pp. 382-414 ◽  
Author(s):  
J M Lowenstein
Keyword(s):  
Ammonia Production ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle

Ammonia and amino acid metabolism in human skeletal muscle during exercise

1992 ◽  
Vol 70 (1) ◽  
pp. 132-141 ◽  
Author(s):  
T. E. Graham ◽  
D. A. MacLean
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Steady State ◽  
Amino Acid ◽  
Human Skeletal Muscle ◽  
Branched Chain Amino Acids ◽  
Ammonia Production ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle ◽  
Branched Chain

This review focuses on the ammonia and amino acid metabolic responses of active human skeletal muscle, with a particular emphasis on steady-state exercise. Ammonia production in skeletal muscle involves the purine nucleotide cycle and the amino acids glutamate, glutamine, and alanine and probably also includes the branched chain amino acids as well as aspartate. Ammonia production is greatest during prolonged, steady state exercise that requires 60–80% [Formula: see text] and is associated with glutamine and alanine metabolism. Under these circumstances it is unresolved whether the purine nucleotide cycle (AMP deamination) is active; if so, it must be cycling with no IMP accumulation. It is proposed that under these circumstances the ammonia is produced from slow twitch fibers by the deamination of the branched chain amino acids. The ammonia response can be suppressed by increasing the carbohydrate availability and this may be mediated by altering the availability of the branched chain amino acids. The fate of the ammonia released into the circulation is unresolved, but there is indirect evidence that a considerable portion may be excreted by the lung in expired air.Key words: glutamine, branched chain amino acids, glutamate dehydrogenase, purine nucleotide cycle.

scholarly journals The purine nucleotide cycle. A pathway for ammonia production in the rat kidney.

1976 ◽  
Vol 58 (2) ◽  
pp. 326-335 ◽  
Author(s):  
R T Bogusky ◽  
L M Lowenstein ◽  
J M Lowenstein
Keyword(s):  
Rat Kidney ◽  
Ammonia Production ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle

Ammonia Production in Muscle: The Purine Nucleotide Cycle

Science ◽  
1971 ◽  
Vol 171 (3969) ◽  
pp. 397-400 ◽  
Author(s):  
J. Lowenstein ◽  
K. Tornheim
Keyword(s):  
Ammonia Production ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle

Contribution of purine nucleotide cycle to intranephron ammoniagenesis in rats

1988 ◽  
Vol 255 (6) ◽  
pp. F1122-F1127
Author(s):  
K. Tamura ◽  
H. Endou
Keyword(s):  
Amino Acids ◽  
Metabolic Acidosis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Specific Inhibitor ◽  
Ammonia Production ◽  
Purine Nucleotide ◽  
Nephron Segments ◽  
A Value ◽  
Purine Nucleotide Cycle ◽  
High Concentrations

To evaluate the contribution of the purine nucleotide cycle (PNC) in renal ammoniagenesis, ammonia production (AP) in cortical tubular suspensions and microdissected nephron segments of control and acidotic rats was determined using various amino acids, including glutamine (Gln) and aspartate (Asp). In the cortical tubular suspensions, the best substrate for ammoniagenesis was Gln (153.1 +/- 19.4 nmol.mg protein-1.15 min-1) followed by Asp (70.9 +/- 11.4). Metabolic acidosis resulted in a significant increase of AP only from Gln (316.5 +/- 36.1 nmol.mg protein-1.15 min-1, P less than 0.01 vs. control). Intranephron distribution of AP (pmol/mm or a glomerulus/15 min) from Gln showed that the first segment of the proximal tubule (S1) was highest in control (95.7 +/- 9.0), and its AP markedly increased in acidosis (221.6 +/- 8.3, P less than 0.001 vs. control). The most interesting and striking finding was that with Asp as a substrate, AP was maximal in S1 (165.0 +/- 32.8), with a value exceeding that from Gln. An adenylosuccinase inhibitor, 6-mercaptopurine (0.1 mM), significantly inhibited AP from Asp in S1 and S3, and from Gln in S1. On the contrary, a specific inhibitor of phosphoenolpyruvate carboxykinase, 3-mercaptopicolinate (0.1 mM), caused a significant decrease of AP from Gln, but not from Asp, in S1. From these results it could be concluded that AP via PNC can occur at high rates, especially in S1, only when Asp is present at high concentrations.

scholarly journals The Purine Nucleotide Cycle

1972 ◽  
Vol 247 (1) ◽  
pp. 162-169 ◽  
Author(s):  
Keith Tornheim ◽  
John M. Lowenstein
Keyword(s):  
Purine Nucleotide ◽  
Purine Nucleotide Cycle

scholarly journals The role of glutamine oxidation and the purine nucleotide cycle for adaptation of tumour energetics to the transition from the anaerobic to the aerobic state

1988 ◽  
Vol 252 (2) ◽  
pp. 381-386 ◽  
Author(s):  
Z Kovacević ◽  
D Jerance ◽  
O Brkljac
Keyword(s):  
Adenine Nucleotide ◽  
The Other ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle ◽  
Adenine Nucleotide Pool

It is proposed that the purine nucleotide cycle and glutamine oxidation play a key role in the adaptation of tumour energetics to the transition from the anaerobic to the aerobic state. In support of this proposal, it was found that glutamine and inosine markedly increase total adenylates in the presence of oxygen, whereas the addition of hadacidin abolishes this effect. Transition of the cells from the anaerobic to the aerobic state, and vice versa, in the presence of glutamine plus inosine revealed that there are two components of the adenine nucleotide pool, one which is stable and the other which is variable and responds to the aerobic-anaerobic transition. This part of the pool undergoes degradation or resynthesis owing to activation of the enzymes of the purine nucleotide cycle. Resynthesis of the pool is accompanied by substantial net utilization of aspartate, which is produced by glutamine oxidation. This is supported by the experiments in which the cells were alternately incubated with nitrogen or oxygen, demonstrating that hadacidin significantly decreased utilization of aspartate and regeneration of ATP owing to inhibition of adenylosuccinate synthase.

Binding of adenylosuccinate synthetase to contractile proteins of muscle

1989 ◽  
Vol 257 (1) ◽  
pp. C29-C35 ◽  
Author(s):  
J. P. Manfredi ◽  
R. Marquetant ◽  
A. D. Magid ◽  
E. W. Holmes
Keyword(s):  
Ionic Strength ◽  
Dissociation Constant ◽  
Thin Filament ◽  
Contractile Proteins ◽  
Purine Nucleotide ◽  
Apparent Dissociation Constant ◽  
Thin Filaments ◽  
Adenylosuccinate Synthetase ◽  
Purine Nucleotide Cycle ◽  
Low Ionic Strength

The muscle isozyme of adenylosuccinate synthetase (AdSS), an enzyme of the purine nucleotide cycle, has previously been shown to bind to purified F-actin in buffers of low ionic strength and pH (Ogawa et al. Eur. J. Biochem. 85: 331-338, 1978). We have extended these observations by measuring the association of both crude and purified AdSS with the contractile proteins of muscle in buffers of physiological ionic strength and pH. Under these conditions, the enzyme binds to F-actin, actin-tropomyosin complexes, reconstructed thin filaments, and myofibrils but not to myosin. The apparent dissociation constant of 1.2 microM and binding maximum of 2.6 nmol enzyme/mg myofibrils indicate that binding of AdSS to myofibrils can be physiologically significant. The results suggest that AdSS in muscle may be associated with the thin filament of myofibrils.

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