title: Effects of age and calorie restriction on tryptophan nitration, protein content, and activity of succinyl-CoA:3-ketoacid CoA transferase in rat kidney mitochondria.
abstract: This study examined the protein targets of nitration and the consequent impact on protein function in rat kidney mitochondria at 4, 13, 19, and 24 months of age. Succinyl-CoA transferase (SCOT), a rate-limiting enzyme in the degradation of ketone bodies, was the most intensely reactive protein against anti-3-nitrotyrosine antibody in rat kidney mitochondria. However, subsequent mass spectrometric and amino acid analyses of purified SCOT indicated that tryptophan 372, rather than a tyrosine residue, was the actual site of simultaneous additions of nitro and hydroxy groups. This finding suggests that identification of nitrated tyrosine residues based solely on reactivity with anti-3-nitrotyrosine antibody can be potentially misleading. Between 4 and 24 months of age, the amounts of SCOT protein and catalytic activity, expressed per milligram of mitochondrial proteins, decreased by 55 and 45%, respectively. SCOT, and particularly its nitrated carboxy-terminal region, was relatively more susceptible to in vitro proteolysis than other randomly selected kidney mitochondrial proteins. The age-related decreases in SCOT protein amount and catalytic activity were prevented by a relatively long-term 40% reduction in the amount of food intake. Loss of SCOT protein in the aged rats may attenuate the capacity of kidney mitochondria to utilize ketone bodies for energy production.
authors.affiliation: Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Brégère
authors.forename: Igor
authors.initials: I
authors.lastname: Rebrin
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Gallaher
authors.forename: Rajindar S
authors.initials: RS
authors.lastname: Sohal
mesh_terms: D000367:Age Factors; D000375:Aging; D000818:Animals; D031204:Caloric Restriction; D020134:Catalytic Domain; D015256:Coenzyme A-Transferases / Q000378:metabolism*; D007659:Ketones / Q000378:metabolism; D007668:Kidney / Q000201:enzymology* / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008928:Mitochondria / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry*; D051381:Rats; D011916:Rats, Inbred F344; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D007659:Ketones; D014364:Tryptophan; D015256:Coenzyme A-Transferases; C021460:3-ketoacid CoA-transferase; D009584:Nitrogen