Age-related changes in subunit composition and regulation of hepatic 6-phosphofructo-1-kinase.
6-Phosphofructo-1-kinase (PFK) isoenzyme pools from livers of fetal, neonatal, young adult (3 months) and aged (24 months) rats were studied. Near-term liver PFK isoenzyme pools were composed of nearly equal quantities of all three subunits. During the 30 days after birth, the total activity increased by 25%; the amount of the L-type, M-type or C-type subunit was increased 3-fold, was unchanged, or was decreased by 80% respectively. In aged rats, compared with young adults, total PFK activity was unchanged, but the L-type, M-type or C-type subunit decreased by 24%, increased by 39%, or increased by 338% respectively. During neonatal maturation, the changing subunit composition of the hepatic isoenzyme pools led to a decreased susceptibility to ATP inhibition, to a greater apparent affinity for fructose 6-phosphate, and to increased sensitivity to fructose 2,6-bisphosphate. Also, these alterations correlated with the measured increases in fructose 2,6-bisphosphate and the reported optimal rate of hepatic glycolysis/gluconeogenesis.
Dunaway
G A
GA
Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62708.
Kasten
T P
TP
Crabtree
S
S
Mhaskar
Y
Y
D000375:Aging; D000818:Animals; D005260:Female; D005333:Fetus; D005635:Fructosediphosphates / Q000378:metabolism; D006019:Glycolysis; D007527:Isoenzymes / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains
D005635:Fructosediphosphates; D007527:Isoenzymes; C027652:fructose 2,6-diphosphate; D010732:Phosphofructokinase-1