ATP-stimulated protease activity in brown fat mitochondria: response to a 24-h fast in mice.
Brown fat mitochondria have [3H]casein-hydrolyzing activity at pH 8.0 associated with both membrane and soluble fractions. An ATP-stimulated proteolytic activity inhibited by vanadate and N-ethylmaleimide was found in the soluble fraction. Membrane-associated proteolytic activity was inhibited by phenylmethylsulfonyl fluoride and trypsin inhibitor, suggesting that it is a serine protease. A 24-h fast in mice caused a significant loss of mitochondrial proteins from the tissue, but had no effect on protease activity of isolated mitochondria with or without ATP. The ATP-stimulated release of amino acids or peptides from isolated mitochondria, as measured with fluorescamine, was not influenced by food deprivation. Thus, brown fat mitochondria possess an ATP-stimulated proteolytic pathway that does not appear to be involved in the bulk removal of mitochondrial proteins from brown fat of fasting mice.
Desautels
M
M
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002001:Adipose Tissue, Brown / Q000201:enzymology*; D000818:Animals; D010450:Endopeptidases / Q000187:drug effects*; D005215:Fasting; D051379:Mice; D008928:Mitochondria / Q000201:enzymology*; D013997:Time Factors
D000255:Adenosine Triphosphate; D010450:Endopeptidases