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

Conference · Wed Mar 05 04:00:00 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-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:4
• Country of Publication: United States
• Language: English

Related Subjects

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