Role of ATP in the regulation of branched-chain alpha-keto acid dehydrogenase activity in liver and muscle mitochondria of fed, fasted, and diabetic rats.

The present study was conducted to investigate the metabolic regulation of leucine oxidation during exercise. Ten rats per group were run at 27 m/min (0% grade) on a treadmill for 30 and 120 min or until exhausted, and the total and basal activity of branched-chain keto acid dehydrogenase was examined in the muscle, liver, and heart. The total activity of the dehydrogenase in the heart, liver, or skeletal muscle was unchanged by exercise. However, exercise increased the basal activity levels of the dehydrogenase about 10-fold in muscle and 5-fold in heart. The basal dehydrogenase activity in the liver was unchanged by exercise. Activation of the dehydrogenase in both muscle and heart was statistically elevated after 30 min exercise and continued to increase during the remainder of the exercise bout. The basal activity of the dehydrogenase returned to resting levels by 10 min postexercise. The activation of the dehydrogenase in muscle and heart during exercise likely is due to dephosphorylation because activity of the enzyme in mitochondria isolated from exercised muscles reverts to control values when the mitochondria are incubated in the presence of ATP. Thus the increased leucine oxidation observed during exercise is due to activation of the branched-chain keto acid dehydrogenase by dephosphorylation. This is the first example of a large increase in branched-chain keto acid dehydrogenase activity caused by a physiological process. This demonstrates that the muscle's latent capacity of oxidize branched-chain amino acids is much larger than previously thought and that this capacity is used in exercising muscle.

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NUTRITIONAL STATUS AFFECTS BRANCHED-CHAIN KETO ACID DEHYDROGENASE ACTIVITY DURING EXERCISE IN HUMANS 286

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-199605001-00286 ◽

1996 ◽

Vol 28 (Supplement) ◽

pp. 48

Author(s):

M. J. Gibala ◽

M. L. Jackman ◽

E. Hultman

Keyword(s):

Nutritional Status ◽

Dehydrogenase Activity ◽

Keto Acid ◽

Acid Dehydrogenase ◽

Branched Chain ◽

Exercise In Humans

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Crc Is Involved in Catabolite Repression Control of the bkd Operons of Pseudomonas putida andPseudomonas aeruginosa

Journal of Bacteriology ◽

10.1128/jb.182.4.1144-1149.2000 ◽

2000 ◽

Vol 182 (4) ◽

pp. 1144-1149 ◽

Cited By ~ 85

Author(s):

Kathryn L. Hester ◽

Jodi Lehman ◽

Fares Najar ◽

Lin Song ◽

Bruce A. Roe ◽

...

Keyword(s):

Pseudomonas Putida ◽

Catabolite Repression ◽

Carbon Sources ◽

Keto Acid ◽

Carbon Regulation ◽

Acid Dehydrogenase ◽

Transposon Mutants ◽

Branched Chain ◽

Glucose 6 Phosphate Dehydrogenase

ABSTRACT Crc (catabolite repression control) protein of Pseudomonas aeruginosa has shown to be involved in carbon regulation of several pathways. In this study, the role of Crc in catabolite repression control has been studied in Pseudomonas putida. The bkd operons of P. putida and P. aeruginosa encode the inducible multienzyme complex branched-chain keto acid dehydrogenase, which is regulated in both species by catabolite repression. We report here that this effect is mediated in both species by Crc. A 13-kb cloned DNA fragment containing the P. putida crc gene region was sequenced. Crc regulates the expression of branched-chain keto acid dehydrogenase, glucose-6-phosphate dehydrogenase, and amidase in both species but not urocanase, although the carbon sources responsible for catabolite repression in the two species differ. Transposon mutants affected in their expression of BkdR, the transcriptional activator of thebkd operon, were isolated and identified as crcand vacB (rnr) mutants. These mutants suggested that catabolite repression in pseudomonads might, in part, involve control of BkdR levels.

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