JBC, Vol. 251, Issue 22, 7127-7131, Nov, 1976
6-Phosphogluconate dehydrogenase. Purification and kinetics
M. L. Toews, M. I. Kanji and W. R. Carper
A method is described for the isolation and purification of
6-phosphogluconate dehydrogenase from pig liver. The molecular weight is
estimated at 83,000 and that of the subunits is 42,000 as determined by gel
electrophoresis. The pH maximum is 8.5 in 50 mM glycine/NaOH buffer and
from 7.5 to 10 in 50 mM phosphate buffer at 30 degrees. Magnesium ion is
not required for activity and acts as an inhibitor at concentrations above
20 mM. A cellular fractionation study indicates that this enzyme is located
almost entirely within the soluble portion of the cytoplasm. Kinetic
studies have been done in 50 mM glycine buffer, pH 8.5, at 30 degrees. The
data are consistent with a sequential mechanism in which NADP+ is added
first, followed by 6-phosphogluconate, and the products are released in the
order, CO2, ribulose 5-phosphate, and NADPH. The Michaelis constant is 13.5
muM for 6-phosphogluconate. Dissociation constants are 4.8 muM for NADP+
and 5.1 muM for NADPH.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
