JBC, Vol. 250, Issue 15, 6040-6045, Aug, 1975
Bovine kidney alkaline phosphatase. Purification, subunit structure, and metalloenzyme properties
G. Cathala and C. Brunel
Kidney alkaline phosphatase was purified to homogeneity. It is a
glycoprotein of about 172,000 molecular weight. Analyses of the subunit
structure by sedimentation equilibrium in 6 M guanidine hydrochloride and
by gel electrophoresis in sodium dodecyl sulfate indicate that the alkaline
phosphatase is a dimer comprising two very similar or identical subunits of
about 87,000 molecular weight. The native enzyme contains 4.5 +/- 0.2 g
atoms of zinc per mol of protein. Reconstitution experiments from the
apophosphatase show that binding of 4 Zn2+ per mol of dimer is essential
for full activity. The kinetic data of Zn2+ binding to the apoprotein
require at least a two-step mechanism, in which one of the steps
corresponds to a conformational change within the enzyme. This paper also
presents data concerning amino acid composition, sugar content, enzyme
stability, absorbance index, and sedimentation velocity.