Non-essential activation of rat liver porphobilinogen-deaminase by folic acid.
This report demonstrates the ability of folic acid to activate rat liver porphobilinogen-deaminase (PBG-D). Lineweaver-Burk analysis revealed an increase in Vmax (38%) without affecting the Km. In the concentration range assayed, secondary replots of 1/delta slope and 1/delta intersect versus 1/[folic acid] yielded straight lines, indicating the binding of a single molecule of activator to the enzyme PBG-D, with a KA = 1.66 mM. Results presented here show that folic acid acts as a non-essential activator (alpha = 1; beta = 1.6). The activating effect of folic acid has been observed employing the 35-70% ammonium sulphate precipitated fraction, desalted by dialysis or gel filtration, whereas no action was detected when other partially purified PBG-D preparations were utilized as the enzyme source, suggesting either the presence of sites saturated for the activator, or the existence of a different structural protein conformation, or both.
Noriega
G O
GO
Department of Biochemistry, University of Buenos Aires, Ciudad Universitaria, Argentine.
Juknat
A A
AA
Batlle
A M
AM
D000818:Animals; D002458:Cell Fractionation; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D005492:Folic Acid / Q000494:pharmacology*; D011163:Hydroxymethylbilane Synthase / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008962:Models, Theoretical; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains
D005492:Folic Acid; D011163:Hydroxymethylbilane Synthase