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The soluble high Km form of cyclic nucleotide phosphodiesterase (EC 3.4.1.17) was purified over 2000-fold from bovine brain homogenates principally using blue dextran-Sepharose chromatography. The purified protein has a specific enzymic activity of 167 units/mg and appears homogeneous when examined by polyacrylamide gel electrophoresis. The enzyme has a molecular weight of 1.26 +/- 0.05 x 10(5) consisting of two apparently identical polypeptide chains. Kinetic measurements indicate that the substrates cyclic GMP and cyclic AMP each have a single Km value, 9 +/- 1 micron and 150 +/- 50 micron, respectively, that the two cyclic nucleotides compete for the same catalytic site, that the blue dye of blue dextran-Sepharose is a competitive inhibitor for the cyclic nucleotides, and that the Vmax with cyclic AMP as substrate is about an order of magnitude larger than that for cyclic GMP. Bovine brain calmodulin stimulates the catalytic rate of the purified enzyme in the presence of Ca2+ by increasing the Vmax associated with each cyclic nucleotide substrate.
M E Morrill, and
S T Thompson, and
E Stellwagen
October 1978,
Biochimica et biophysica acta,
M E Morrill, and
S T Thompson, and
E Stellwagen
January 1974,
Methods in enzymology,
M E Morrill, and
S T Thompson, and
E Stellwagen
November 1984,
Biochemical pharmacology,
M E Morrill, and
S T Thompson, and
E Stellwagen
January 1974,
Methods in enzymology,
M E Morrill, and
S T Thompson, and
E Stellwagen
June 1980,
The Journal of biological chemistry,
M E Morrill, and
S T Thompson, and
E Stellwagen
November 1972,
Archives of biochemistry and biophysics,
M E Morrill, and
S T Thompson, and
E Stellwagen
June 1976,
Nature,
M E Morrill, and
S T Thompson, and
E Stellwagen
February 1982,
The Journal of biological chemistry,
M E Morrill, and
S T Thompson, and
E Stellwagen
February 1983,
Biochemistry,
M E Morrill, and
S T Thompson, and
E Stellwagen
November 1976,
Biochemical and biophysical research communications,
