Consumption of soy protein isolate modulates the phosphorylation status of hepatic ATPase/ATP synthase beta protein and increases ATPase activity in rats.
ATPase/ATP synthase plays important roles in the regulation of carbohydrate, protein, and lipid metabolism through modulating energy homeostasis. The purpose of this study was to examine the effects of feeding soy proteins and isoflavones (ISF) on the enzymatic activity and protein modification of hepatic mitochondrial ATPase/ATP synthase. In Expt. 1, Sprague-Dawley rats aged 50 d were fed diets containing either 20% casein or 20% alcohol-washed soy protein isolate (SPI) with or without supplemental ISF (770.7 micromol/kg diet) for 70 d. In Expt. 2, weanling Sprague-Dawley rats were fed diets containing 20% casein with or without added ISF (154.1 micromol/kg diet) or 20% SPI for 90 d. Hepatic mitochondrial ATPase activity was significantly higher in the rats fed SPI than in those fed casein. Addition of ISF to SPI eliminated the action of SPI. ATPase/ATP synthase beta protein contents in the liver were unchanged; however, its patterns measured by 2-dimensional Western blot were different among dietary groups. The rats fed SPI or SPI plus ISF had 3 more major protein spots with the same molecular weights (80 kDa and 55 kDa) as those presented in the rats fed casein but with different isoelectric points. Pretreatment of hepatic mitochondrial proteins from the rats fed casein with alkaline phosphatase produced the same ATPase/ATP synthase beta patterns as observed in the SPI-fed rats and significantly elevated the ATPase activity. These results suggest that consumption of soy proteins increases hepatic ATPase activity, which might be a consequence of increased dephosphorylation or decreased phosphorylation of the mitochondrial ATPase/ATP synthase beta protein.
Mei
Jie
J
Nutrition Research Division, Health Products and Food Branch, Health Canada, Ottawa, Canada K1A 0L2.
Wood
Carla
C
L'abbé
Mary R
MR
Gilani
G Sarwar
GS
Cooke
Gerard M
GM
Curran
Ivan H
IH
Xiao
Chao Wu
CW
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D015180:Electrophoresis, Gel, Two-Dimensional; D007328:Insulin / Q000097:blood; D007526:Isoelectric Point; D008099:Liver / Q000187:drug effects* / Q000201:enzymology*; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D030262:Soybean Proteins / Q000302:isolation & purification / Q000494:pharmacology*
D007328:Insulin; D030262:Soybean Proteins; D000251:Adenosine Triphosphatases; C497342:ATP synthase beta subunit, rat; D025261:Mitochondrial Proton-Translocating ATPases