scholarly journals Effects of dietary protein intake on branched-chain keto acid dehydrogenase activity of the rat. Immunochemical analysis of the enzyme complex.

1988 ◽  
Vol 263 (7) ◽  
pp. 3454-3461
Author(s):  
R H Miller ◽  
R S Eisenstein ◽  
A E Harper
Keyword(s):  
Dehydrogenase Activity ◽  
Dietary Protein ◽  
Protein Intake ◽  
Enzyme Complex ◽  
Immunochemical Analysis ◽  
Dietary Protein Intake ◽  
Keto Acid ◽  
Acid Dehydrogenase ◽  
Branched Chain

Activation of branched-chain keto acid dehydrogenase by exercise

1985 ◽  
Vol 248 (2) ◽  
pp. R166-R171 ◽  
Author(s):  
G. J. Kasperek ◽  
G. L. Dohm ◽  
R. D. Snider
Keyword(s):  
Dehydrogenase Activity ◽  
Metabolic Regulation ◽  
Exercise Bout ◽  
Total Activity ◽  
Activity Levels ◽  
Keto Acid ◽  
Leucine Oxidation ◽  
Basal Activity ◽  
Acid Dehydrogenase ◽  
Branched Chain

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.

scholarly journals Insertional Inactivation of Branched-Chain α-Keto Acid Dehydrogenase in Staphylococcus aureus Leads to Decreased Branched-Chain Membrane Fatty Acid Content and Increased Susceptibility to Certain Stresses

2008 ◽  
Vol 74 (19) ◽  
pp. 5882-5890 ◽  
Author(s):  
Vineet K. Singh ◽  
Dipti S. Hattangady ◽  
Efstathios S. Giotis ◽  
Atul K. Singh ◽  
Neal R. Chamberlain ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Fatty Acid ◽  
Acid Content ◽  
Fatty Acid Content ◽  
Stress Conditions ◽  
Enzyme Complex ◽  
Keto Acid ◽  
Wild Type ◽  
Acid Dehydrogenase ◽  
Branched Chain

ABSTRACT Staphylococcus aureus is a major community and nosocomial pathogen. Its ability to withstand multiple stress conditions and quickly develop resistance to antibiotics complicates the control of staphylococcal infections. Adaptation to lower temperatures is a key for the survival of bacterial species outside the host. Branched-chain α-keto acid dehydrogenase (BKD) is an enzyme complex that catalyzes the early stages of branched-chain fatty acid (BCFA) production. In this study, BKD was inactivated, resulting in reduced levels of BCFAs in the membrane of S. aureus. Growth of the BKD-inactivated mutant was progressively more impaired than that of wild-type S. aureus with decreasing temperature, to the point that the mutant could not grow at 12�C. The growth of the mutant was markedly stimulated by the inclusion of 2-methylbutyrate in the growth medium at all temperatures tested. 2-Methylbutyrate is a precursor of odd-numbered anteiso fatty acids and bypasses BKD. Interestingly, growth of wild-type S. aureus was also stimulated by including 2-methylbutyrate in the medium, especially at lower temperatures. The anteiso fatty acid content of the BKD-inactivated mutant was restored by the inclusion of 2-methylbutyrate in the medium. Fluorescence polarization measurements indicated that the membrane of the BKD-inactivated mutant was significantly less fluid than that of wild-type S. aureus. Consistent with this result, the mutant showed decreased toluene tolerance that could be increased by the inclusion of 2-methylbutyrate in the medium. The BKD-inactivated mutant was more susceptible to alkaline pH and oxidative stress conditions. Inactivation of the BKD enzyme complex in S. aureus also led to a reduction in adherence of the mutant to eukaryotic cells and its survival in a mouse host. In addition, the mutant offers a tool to study the role of membrane fluidity in the interaction of S. aureus with antimicrobial substances.

Sign in / Sign up

Export Citation Format

Share Document