6-Phosphofructo-1-kinase of rat placenta.
6-Phosphofructo-1-kinase (PFK) of rat placenta was purified to homogeneity with a recovery of 56% of the enzyme activity in the original extract. The purified enzyme is a tetramer and the Mr value of the subunit is 85,000 +/- 1500 as shown by gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Considering the properties of the native rat placental PFK isoenzyme, it is clear that this tissue is a complex mixture of homotetramer and heterotetramer. Purified placenta PFK displayed little cooperativity at pH 7.0 with respect to fructose 6-phosphate and was markedly inhibited with high concentrations of ATP. The affinity of the enzyme for fructose 6-phosphate was increased by fructose 2,6-biphosphate. The purified enzyme was highly inhibited by citrate, whereas it was only slightly inhibited by phosphoenol pyruvate. ADP, AMP and fructose 2,6-bisphosphate showed little stimulation towards placental PFK. The present study suggests that the placental PFK is a relatively active enzymic form and it is also probably characterized with a high rate of glycolysis possibly because this tissue requires a high energy production for the development and maintenance of the fetus as the placenta tends to be a semipermeable membrane through which substances are exchanged between mother and fetus.
Khoja
S M
SM
Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
Abuelgassim
A O
AO
Salem
A M
AM
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002850:Chromatography, Gel; D002951:Citrates / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005260:Female; D005635:Fructosediphosphates / Q000378:metabolism; D005636:Fructosephosphates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D009928:Organ Specificity; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010732:Phosphofructokinase-1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010920:Placenta / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains
D002951:Citrates; D005635:Fructosediphosphates; D005636:Fructosephosphates; C027618:fructose-6-phosphate; D010728:Phosphoenolpyruvate; D000255:Adenosine Triphosphate; D010732:Phosphofructokinase-1