Transaminases of branched-chain amino acids

Ichihara, Akira; Takahashi, H

doi:10.1016/0005-2744(68)90206-4

Cited by 26 publications

(17 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Abbreviations used in this paper: BCAA, branched-chain amino acid; BCKA, branched-chain a-keto acid; BCKAD, branched-chain a-keto acid dehydrogenase. their concentrations in blood and tissues rise in direct proportion to the protein content of the diet (3)(4)(5), and (b) BCAA aminotransferase, the initial enzyme in BCAA catabolism, is relatively refractory to changes in dietary protein (6). This apparent lack ofadaptation has prompted some investigators to conclude that the body is unable to maintain the free body pools of BCAA by increasing oxidation during times of surfeit or by decreasing oxidation during times of deficiency.…”

Section: Introductionmentioning

confidence: 99%

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

Block¹,

Aftring²,

Mehard³

et al. 1987

J. Clin. Invest.

View full text Add to dashboard Cite

The effects of dietary protein on the activity of skeletal muscle branched-chain a-keto acid dehydrogenase (BCKAD) were investigated. BCKAD is rate-limiting for branched-chain amino acid (BCAA) catabolism by muscle; its activity is modulated by phosphorylation-dephosphorylation. In rats fed an adequate protein (25% casein) diet, BCKAD was -2% active postabsorptively and increased to 10% or 16% active after a 25% or 50% protein meal, respectively. Prolonged feeding of a 50% protein diet increased postabsorptive BCKAD activity to 7% with further increases to 40% active postprandially. On a low protein (9% casein) diet BCKAD remained -2% active regardless of meal-feeding. Dose-dependent activation of BCKAD by intravenous leucine in postabsorptive rats was blunted by a low protein diet. We conclude that excesses of dietary protein enhance the capacity of skeletal muscle to oxidize BCAA, muscle conserves BCAA when protein intake is inadequate, and skeletal muscle may play an important role in whole-body BCAA homeostasis.

show abstract

Section: Introductionmentioning

confidence: 99%

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

Block¹,

Aftring²,

Mehard³

et al. 1987

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

“…In de novo biosynthesis of valine, the two enzymes will compete directly for 2-oxoisovalerate, and the most likely possible control is thus kinetic. No & values for branched-chain keto acids seem to have been reported, either for pyruvate decarboxylase or for any branched-chain amino acid aminotransferase (Ichihara, 1985), so it is not possible to predict the outcome of such competition. Our conclusion also implies that a transport mechanism must exist to allow de novo synthesized branched-chain keto acids to leave the mitochondria where they have been made (Ryan & Kohlhaw, 1974).…”

Section: Subcellular Location Of the Enzymes Of The Ehrlich Pathway Dmentioning

confidence: 99%

Activities of the enzymes of the Ehrlich pathway and formation of branched-chain alcohols in Saccharomyces cerevisiae and Candida utilis grown in continuous culture on valine or ammonium as sole nitrogen source

Derrick

Large²

1993

Journal of General Microbiology

View full text Add to dashboard Cite

“…For instance, a number of the mammalian BcATs are specific for only one of the BCAAs (1,11,14), while the methanococcal and other bacterial enzymes have little preference among the BCAAs (4,16,21,31,40). Similarly, the activity of the methanococcal and other bacterial BcATs towards the ArAAs is usually within an order of magnitude of the activity towards the BCAAs.…”

mentioning

confidence: 99%

“…Similarly, the activity of the methanococcal and other bacterial BcATs towards the ArAAs is usually within an order of magnitude of the activity towards the BCAAs. For the mammalian BcATs, activity towards the ArAAs is frequently absent (11). Likewise, the apparent molecular weight of the mammalian BcATs, Mr = 42,000 to 75,000, is much smaller than that of methanococcal and other bacterial enzymes, Mr = 130,000 to 195,000 (21,22,29).…”

mentioning

confidence: 99%

Characterization of amino acid aminotransferases of Methanococcus aeolicus

Xing

Whitman

1992

J Bacteriol

View full text Add to dashboard Cite

Four aminotransferases were identified and characterized from Methanococcus aeolicus. Branched-chain aminotransferase (BcAT, EC 2.6.1.42), aspartate aminotransferase (AspAT, EC 2.6.1.1), and two aromatic aminotransferases (EC 2.6.1.57) were partially purified 175-, 84-, 600-, and 30-fold, respectively. The apparent molecular weight, substrate specificity, and kinetic properties of the BcAT were similar to those of other microbial BcATs. The AspAT had an apparent molecular weight of 162,000, which was unusually high. It had also a broad substrate specificity, which included activity towards alanine, a property which resembled the enzyme from Sulfolobus solfataricus. An additional alanine aminotransferase was not found in M. aeolicus, and this activity of AspAT could be physiologically significant. The apparent molecular weights of the aromatic aminotransferases (ArAT-I and ArAT-II) were 150,000 and 90,000, respectively. The methanococcal ArATs also had different pIs and kinetic constants. ArAT-I may be the major ArAT in methanococci. High concentrations of 2-ketoglutarate strongly inhibited valine, isoleucine, and alanine transaminations but were less inhibitory for leucine and aspartate transaminations. Aromatic amino acid transaminations were not inhibited by 2-ketoglutarate. 2-Ketoglutarate may play an important role in the regulation of amino acid biosynthesis in methanococci.

show abstract

Transaminases of branched-chain amino acids

Cited by 26 publications

References 21 publications

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

Activities of the enzymes of the Ehrlich pathway and formation of branched-chain alcohols in Saccharomyces cerevisiae and Candida utilis grown in continuous culture on valine or ammonium as sole nitrogen source

Characterization of amino acid aminotransferases of Methanococcus aeolicus

Contact Info

Product

Resources

About