Differences in properties of cytosol and membrane-derived protein kinases

Adenosine 3':5'-monophosphate-dependent protein kinase present in membrane fractions of bovine brain, heart, liver, and muscle was solubilized with Triton X-100. Certain properties of the membrane-derived enzyme were compared with those of two adenosine 3':5'-monophosphate-dependent protein kinases present in the cytosol fractions from each of the same tissues. The properties studied included chromatographic behavior on DEAE-cellulose columns, specificity with respect to substrate proteins, and sensitivity to NaCl and Triton X-100. The membrane-derived enzyme from each tissue had properties similar to those of the membrane-derived enzyme from each of the other tissues. Moreover, the cytosol enzymes from each tissue had properties similar to those of the corresponding enzymes in the cytosol from each of the other tissues. However, for any given tissue, the properties of the membrane-derived enzyme differed from those of the cytosol enzymes, possibly reflecting different functional roles for the membrane-bound and cytosol enzymes.