scholarly journals Branched-chain amino acid oxidation in relation to catabolic enzyme activities in rats given aprotein-free diet at different stages of development

1974 ◽  
Vol 32 (3) ◽  
pp. 615-623 ◽  
Author(s):  
R. D. Sketcher ◽  
W. P. T. James
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Female Rats ◽  
Acid Oxidation ◽  
Stages Of Development ◽  
Oxidation Rates ◽  
Acid Dehydrogenase ◽  
Stage Of Development ◽  
The Difference ◽  
Branched Chain

1. The capacity of animals to conserve branched-chain amino acids was assessed during 3 weeks on a protein-free (PF) diet in groups of female rats at three stages of development, i.e. at weaning (35 g), in a period of rapid growth (85 g) and at maturity (200 g).2. Leucine and valine oxidation was assessed by monitoring the evolution of 14CO2 from a tracer dose of the [1-14C]-labelled L-amino acid given intragastrically. Activities of the L-leucine:2-ketoglutarate aminotransferase (EC 2.6.1.6) and α-keto acid dehydrogenase enzymes in leucine and valine metabolism were also determined in muscle and liver at weekly intervals.3. All three groups of rats given a normal protein intake excreted the same proportion of the dose of labelled leucine and valine. In rats given PF diet there was a consistent reduction in 14CO2 output from both L-[1-14C]leucine and L-[1-14C]valine, but valine was not conserved as efficiently as leucine.4. Muscle dehydrogenase responded to a PF diet in all three groups of rats, but the most marked changes occurred in the youngest group. In addition, there was a decrease in hepatic dehydrogenase activities for leucine and valine catabolism in the weanling group; in older animals there was little change in the α-keto-isovalerate, but a consistent decrease in the activity of the α-keto-isocaproic acid dehydrogenase. The difference in the responsiveness of the dehydrogenases, therefore, matched the difference between leucine and valine oxidation rates in vivo.5. Weanling animals responded rather more efficiently than the older animals to the need to conserve amino acids and there was no evidence of a poorly developed system for adapting to PF intake at this early stage of development.6. Despite reduced catabolism of the amino acids, aminotransferase activities in liver and muscle rose in the first 1–2 weeks on a PF regimen. Aminotransferase activity as such is unlikely to control acid oxidation.

scholarly journals Increase of the activity state and loss of total activity of the branched-chain 2-oxo acid dehydrogenase in rat diaphragm during incubation

1984 ◽  
Vol 224 (2) ◽  
pp. 491-496 ◽  
Author(s):  
A J M Wagenmakers ◽  
J T Schepens ◽  
J H Veerkamp
Keyword(s):  
Amino Acids ◽  
Citrate Synthase ◽  
Ketone Bodies ◽  
Total Activity ◽  
Acid Oxidation ◽  
Oxidation Rates ◽  
Acid Dehydrogenase ◽  
Activity State ◽  
Branched Chain

Actual and total branched-chain 2-oxo acid dehydrogenase activities were determined in homogenates of incubated diaphragms from fed and starved rats. Incubation in Krebs-Ringer buffer increased the activity state, but caused considerable loss of total activity. Palmitate oxidation rates and citrate synthase activities did not significantly change on incubation. Starved muscles showed a higher extent of activation after 15 min of incubation (not after 30 and 60 min) and a smaller loss of total activity. Experiments with the transaminase inhibitor amino-oxyacetate confirm that the contribution of endogenous amino acids to the oxidation precursor pool is also smaller in diaphragms from starved rats on incubation in vitro. These phenomena together cause the higher 14CO2 production from 14C-labelled branched-chain amino acids and 2-oxo acids in muscles from starved than from fed rats. High concentrations of branched-chain 2-oxo acids, and the presence of 2-chloro-4-methyl-pentanoate, octanoate or ketone bodies, increase the extent of activation of the dehydrogenase complex; glucose and pyruvate had no effect. The observed changes of the activity state by these metabolites are discussed in relation to their interaction with branched-chain 2-oxo acid oxidation in incubated hemidiaphragms.

scholarly journals The case for regulating indispensable amino acid metabolism: the branched-chain α-keto acid dehydrogenase kinase-knockout mouse

2006 ◽  
Vol 400 (1) ◽  
Author(s):  
Susan M. Hutson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Essential Amino Acids ◽  
The Body ◽  
Keto Acid ◽  
Acid Dehydrogenase ◽  
Indispensable Amino Acid ◽  
Branched Chain

BCAAs (branched-chain amino acids) are indispensable (essential) amino acids that are required for body protein synthesis. Indispensable amino acids cannot be synthesized by the body and must be acquired from the diet. The BCAA leucine provides hormone-like signals to tissues such as skeletal muscle, indicating overall nutrient sufficiency. BCAA metabolism provides an important transport system to move nitrogen throughout the body for the synthesis of dispensable (non-essential) amino acids, including the neurotransmitter glutamate in the central nervous system. BCAA metabolism is tightly regulated to maintain levels high enough to support these important functions, but at the same time excesses are prevented via stimulation of irreversible disposal pathways. It is well known from inborn errors of BCAA metabolism that dysregulation of the BCAA catabolic pathways that leads to excess BCAAs and their α-keto acid metabolites results in neural dysfunction. In this issue of Biochemical Journal, Joshi and colleagues have disrupted the murine BDK (branched-chain α-keto acid dehydrogenase kinase) gene. This enzyme serves as the brake on BCAA catabolism. The impaired growth and neurological abnormalities observed in this animal show conclusively the importance of tight regulation of indispensable amino acid metabolism.

Oxidation of 2-oxoisocaproate and 2-oxoisovalerate by the perfused rat heart. Interactions with fatty acid oxidation

1990 ◽  
Vol 68 (1) ◽  
pp. 260-265 ◽  
Author(s):  
Joan Letto ◽  
John T. Brosnan ◽  
Margaret E. Brosnan
Keyword(s):  
Amino Acids ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Branched Chain Amino Acids ◽  
Acid Oxidation ◽  
Perfused Heart ◽  
Acid Dehydrogenase ◽  
Liver And Kidney ◽  
Labelled Compound ◽  
Branched Chain

The interactions between fatty acid oxidation and the oxidation of the 2-oxo acids of the branched chain amino acids were studied in the isolated Langendorff-perfused heart. 2-Oxoisocaproate inhibited the oxidation of oleate, but 2-oxoisovalerate and 2-oxo-3-methylvalerate did not. This difference was not attributable to the magnitude of the flux through the branched chain 2-oxo acid dehydrogenase, which was slightly higher with 2-oxoisovalerate than with 2-oxoisocaproate. Oxidation of 2-oxoisocaproate in the perfused heart was virtually complete, since more than 80% of the isovaleryl-CoA formed from 2-oxo[1-14C]isocaproate was further metabolized to CO2, as determined by comparing 14CO2 production from 2-oxo[14C(U)]isocaproate with that from the 1-14C-labelled compound. Only twice as much 14CO2 was produced from 2-oxo[14C(U)]isovalerate as from the 1-14C-labelled compound, indicating incomplete oxidation. This was confirmed by the accumulation in the perfusion medium of substantial quantities of labelled 3-hydroxyisobutyrate (an intermediate in the pathway of valine catabolism), when hearts were perfused with 2-oxo[14C(U)]isovalerate. The failure of 2-oxoisovalerate to inhibit fatty acid oxidation, then, can be attributed to the fact that its partial metabolism in the heart produces little ATP. We have previously shown that 3-hydroxyisobutyrate is a good gluconeogenic substrate in liver and kidney, and postulate that 3-hydroxyisobutyrate serves as an interorgan metabolite such that valine can serve as a glucogenic amino acid, even when its catabolism proceeds beyond the irreversible 2-oxo acid dehydrogenase in muscle.Key words: branched chain amino acids, branched chain 2-oxoacids, perfused heart, fatty acid metabolism, 3 -hydroxyisobutyrate.

scholarly journals Resolution of branched-chain oxo acid dehydrogenase complex of Pseudomonas aeruginosa PAO.

1986 ◽  
Vol 233 (3) ◽  
pp. 737-742 ◽  
Author(s):  
V McCully ◽  
G Burns ◽  
J R Sokatch
Keyword(s):  
Escherichia Coli ◽  
Heat Treatment ◽  
Amino Acids ◽  
Pseudomonas Aeruginosa ◽  
Amino Acid ◽  
Acid Dehydrogenase ◽  
Lipoamide Dehydrogenase ◽  
Branched Chain ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

Branched-chain oxo acid dehydrogenase was purified from Pseudomonas aeruginosa strain PAO with the objective of resolving the complex into its subunits. The purified complex consisted of four proteins, of Mr 36,000, 42,000, 49,000 and 50,000. The complex was resolved by heat treatment into the 49,000 and 50,000-Mr proteins, which were separated by chromatography on DEAE-Sepharose. The 49,000-Mr protein was identified as the E2 subunit by its ability to catalyse transacylation with a variety of substrates, with dihydrolipoamide as the acceptor. P. aeruginosa, like P. putida, produces two lipoamide dehydrogenases. One, the 50,000-Mr protein, was identified as the specific E3 subunit of branched-chain oxo acid dehydrogenase and had many properties in common with the lipoamide dehydrogenase LPD-val of P. putida. The second lipoamide dehydrogenase had Mr 54,000 and corresponded to the lipoamide dehydrogenase LPD-glc of P. putida. Fragments of C-terminal CNBr peptides of LPD-val from P. putida and P. aeruginosa corresponded closely, with only two amino acid differences over 31 amino acids. A corresponding fragment at the C-terminal end of lipoamide dehydrogenase from Escherichia coli also showed extensive homology. All three peptides had a common segment of eight amino acids, with the sequence TIHAHPTL. This homology was not evident in any other flavoproteins in the Dayhoff data base which suggests that this sequence might be characteristic of lipoamide dehydrogenase.

scholarly journals The effect of starvation on branched-chain 2-oxo acid oxidation in rat muscle

1984 ◽  
Vol 219 (1) ◽  
pp. 253-260 ◽  
Author(s):  
A J M Wagenmakers ◽  
J H Veerkamp
Keyword(s):  
Amino Acid ◽  
Protein Degradation ◽  
Specific Radioactivity ◽  
Acid Oxidation ◽  
Oxidative Decarboxylation ◽  
Precursor Pool ◽  
Oxidation Rates ◽  
Branched Chain Amino Acid ◽  
Endogenous Protein ◽  
Branched Chain

Oxidative-decarboxylation rates of branched-chain amino acids in rat hemidiaphragm and of branched-chain 2-oxo acids in hemidiaphragm, soleus muscle and heart slices of 110-120 g rats were increased considerably by 3-4 days of starvation, when they were calculated from the specific radioactivity in the medium. When the supply from endogenous protein degradation to the oxidation-precursor pool was severely limited by transaminase inhibitors, oxidative-decarboxylation rates of branched-chain 2-oxo acids rose significantly. Since this apparent increase was relatively larger in preparations from fed rats than from 3-days-starved rats, the differences in oxidation rates with nutritional state became less or even not significant. With rat heart the smaller dilution of the oxidation precursor pool after starvation is in accordance with the reported decrease in protein breakdown. Since protein degradation increases with starvation in skeletal muscles, we suggest that the amino acid pool arising from protein degradation is more segregated from the oxidation precursor pool in muscles from starved than from fed rats. We conclude that starvation increases branched-chain amino acid and 2-oxo acid oxidation in skeletal and cardiac muscle considerably less than has been suggested by previous studies.

scholarly journals Interactions among the branched-chain amino acids and their effects on methionine utilization in growing pigs: effects on plasma amino– and keto–acid concentrations and branched-chain keto-acid dehydrogenase activity

2000 ◽  
Vol 83 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Stefan Langer ◽  
Peter W. D. Scislowski ◽  
David S. Brown ◽  
Peter Dewey ◽  
Malcolm F. Fuller
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Plasma Concentrations ◽  
Biceps Femoris ◽  
Branched Chain Amino Acids ◽  
Growing Pigs ◽  
Keto Acid ◽  
Blood Samples ◽  
Acid Dehydrogenase ◽  
Branched Chain

The present experiment was designed to elucidate the mechanism of the methionine-sparing effect of excess branched-chain amino acids (BCAA) reported in the previous paper (Langer & Fuller, 2000). Twelve growing gilts (30–35 kg) were prepared with arterial catheters. After recovery, they received for 7 d a semipurified diet with a balanced amino acid pattern. On the 7th day blood samples were taken before (16 h postabsorptive) and after the morning meal (4 h postprandial). The animals were then divided into three groups and received for a further 7 d a methionine-limiting diet (80 % of requirement) (1) without any amino acid excess; (2) with excess leucine (50 % over requirement); or (3) with excesses of all three BCAA (leucine, isoleucine, valine, each 50 % over the requirement). On the 7th day blood samples were taken as in the first period, after which the animals were killed and liver and muscle samples taken. Plasma amino acid and branched-chain keto acid (BCKA) concentrations in the blood and branched-chain keto-acid dehydrogenase (BCKDH; EC 1.2.4.4) activity in liver and muscle homogenates were determined. Compared with those on the balanced diet, pigs fed on methionine-limiting diets had significantly lower (P < 0·05) plasma methionine concentrations in the postprandial but not in the postabsorptive state. There was no effect of either leucine or a mixture of all three BCAA fed in excess on plasma methionine concentrations. Excess dietary leucine reduced (P < 0·05) the plasma concentrations of isoleucine and valine in both the postprandial and postabsorptive states. Plasma concentrations of the BCKA reflected the changes in the corresponding amino acids. Basal BCKDH activity in the liver and total BCKDH activity in the biceps femoris muscle were significantly (P < 0·05) increased by excesses of leucine or all BCAA.

Regulation of Skeletal Muscle Amino Acid Metabolism during Exercise

2001 ◽  
Vol 11 (1) ◽  
pp. 87-108 ◽  
Author(s):  
Martin J. Gibala
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Amino Acid ◽  
Prolonged Exercise ◽  
Tca Cycle ◽  
Maximal Activity ◽  
Causative Factor ◽  
Acid Oxidation ◽  
Intense Exercise ◽  
Branched Chain

The contribution of amino acid oxidation to total energy expenditure is negligible during short-term intense exercise and accounts for 3–6% of the total adenosine triphosphate supplied during prolonged exercise in humans. While not quantitatively important in terms of energy supply, the intermediary metabolism of several amino acids—notably glutamate, alanine, and the branched-chain amino acids—afreets other metabolites .including the intermediates within the tricarboxylic acid (TCA) cycle. Glutamate appears to be a key substrate for the rapid increase in muscle TCA cycle intermediates (TCAI) that occurs at the onset of moderate to intense exercise, due to a rightward shift of the reaction catalyzed by alanine aminotransferase (glutamate + pyruvate <-> alanine + 2-oxoglutarate). The pool of muscle TCAI declines during prolonged exercise, and this has been attributed to an increase in leucine oxidation that relies on one of the TCAI. However, this mechanism does not appear to be quantitatively important due of the relatively low maximal activity of branched-chain oxoacid dehydrogenase, the key enzyme involved. It has been suggested that an increase in TCAI is necessary to attain high rates of aerobic energy production and that a decline in TCAI may be a causative factor in local muscle fatigue. These topics remain controversial, but recent evidence suggests that changes in TCAI during exercise are unrelated to oxidative energy provision in skeletal muscle.

Glucocorticoid-mediated activation of muscle branched-chain alpha-keto acid dehydrogenase in vivo

1987 ◽  
Vol 252 (3) ◽  
pp. E396-E407 ◽  
Author(s):  
K. P. Block ◽  
W. B. Richmond ◽  
W. B. Mehard ◽  
M. G. Buse
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Active Enzyme ◽  
Acid Oxidation ◽  
Enzyme Complex ◽  
Keto Acid ◽  
Amino Acid Oxidation ◽  
Acid Dehydrogenase ◽  
Branched Chain Amino Acid ◽  
Branched Chain

Muscle branched-chain alpha-keto acid dehydrogenase, the rate-limiting enzyme for branched-chain amino acid oxidation in skeletal muscle, was measured after treatment of rats with glucocorticoids. Cortisone treatment (10 mg X 100 g body wt-1 X day-1 for 2–5 days) resulted in an approximate doubling of the percentage of active enzyme. To further characterize this effect, the enzyme complex was measured 4 h after the intraperitoneal injection of 6 alpha-methylprednisolone, a water-soluble glucocorticoid with rapid onset effects. The percentage of active enzyme increased linearly as the dose of methylprednisolone was increased from 0.125 to 12.5 mg/100 g body wt, while total enzyme activity was unchanged. Administration of insulin with glucose had no significant effect on the activity of the enzyme. However, treatment of rats with insulin and glucose after methylprednisolone administration partially blocked branched-chain alpha-keto acid dehydrogenase activation. The activity of the enzyme complex was correlated with the concentration of leucine in plasma and muscle. Activation of skeletal muscle branched-chain alpha-keto acid dehydrogenase by increased glucocorticoids may play a role in the acceleration of branched-chain amino acid oxidation observed during severe stress.

scholarly journals Interference by branched-chain amino acids in the assay of alanine with alanine dehydrogenase

1978 ◽  
Vol 174 (3) ◽  
pp. 1079-1082 ◽  
Author(s):  
P Lund ◽  
G Baverel
Keyword(s):  
Amino Acids ◽  
Bacillus Subtilis ◽  
Amino Acid ◽  
Dehydrogenase Activity ◽  
Branched Chain Amino Acids ◽  
Acid Dehydrogenase ◽  
Alanine Dehydrogenase ◽  
Amino Acid Dehydrogenase ◽  
Branched Chain Amino Acid ◽  
Branched Chain

Commercial preparations of alanine dehydrogenase from Bacillus subtilis are contaminated to varying extents with activity towards branched-chain amino acids. The Km values for these amino acids are of the same order as for L-alanine (about 10(-3)M). The branched-chain amino acid dehydrogenase activity is lost on dialysis for 2–4h against water or 2mM-EDTA.

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