Transamination of branched chain amino acids (BCAA) in rat adipose tissue

Conference · Wed Mar 05 00:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:7034041

Frick, G P; Goodman, H M

Like most extrahepatic tissues, adipose tissue can transaminate the BCAA faster than they are oxidized. Catabolism of the BCAA by adipose tissue appears to be limited by the activity of branched chain ..cap alpha..-keto acid dehydrogenase (BCDH). Conditions which stimulate the activity of this intramitochondrial enzyme in tissue extracts also increase the rate at which (1-/sup 14/C)leucine (L) and (1-/sup 14/C)valine (V) are oxidized by tissue segments. However, when maximum rates of oxidation were measured, 10 mM L was oxidized to /sup 14/CO/sub 2/ 5 times faster than 10 mM V (30 +/- 2 vs. 6 +/- 1 nmol min/sup -1/ g tis/sup -1/). In contrast, the ..cap alpha..-keto analogs of L and V were oxidized by tissue segments at nearly equal rates which slightly exceeded the rate of L oxidation. These results suggested that transamination might limit the catabolism of V, perhaps due to its inaccessibility to transaminase. The distribution of transaminase activity in tissue extracts was determined after centrifugation to obtain mitochondrial and cytosolic fractions. L and V were transaminated at similar rates by enzymes in both fractions. Transaminase activity in the mitochondrial fraction was greater than that of the cytosol and exceeded the capacity of the tissue to oxidize L. Catabolism of BCAA may depend upon intramitochondrial transamination and oxidation of V may be slower than that of L because uptake of V by mitochondria may be slower than that of L.

• Research Organization: Univ. of Massachusetts Medical School, Worcester
• OSTI ID: 7034041
• Report Number(s): CONF-8604222-; TRN: 87-010472
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:4; Conference: 70. annual meeting of the Federation of American Society for Experimental Biology, St. Louis, MO, USA, 13 Apr 1986
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
CATABOLISM
AMINOTRANSFERASES
ENZYME ACTIVITY
OXIDOREDUCTASES
ADIPOSE TISSUE
CARBON 14 COMPOUNDS
LEUCINE
MITOCHONDRIA
RATS
TRACER TECHNIQUES
VALINE
ANIMAL TISSUES
ANIMALS
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CONNECTIVE TISSUE
ENZYMES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
METABOLISM
NITROGEN TRANSFERASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANOIDS
RODENTS
TISSUES
TRANSFERASES
VERTEBRATES
550501* - Metabolism- Tracer Techniques