TEMPERATURE-HYDROSTATIC PRESSURE STUDIES ON PARTIALLY PURIFIED INORGANIC PYROPHOSPHATASE ACTIVITY.

Morita, Richard Y. (Oregon State University, Corvallis), and Paul F. Mathemeier. Temperature-hydrostatic pressure studies on partially purified inorganic pyrophosphatase activity. J. Bacteriol. 88:1667-1671. 1964.-Partially purified inorganic pyrophosphatase from Bacillus stearothermophilus demonstrated increased activity at 90 C with hydrostatic pressures of 100 to 1,100 atm. At 90 C, optimal activity was at 700 atm. No enzyme activity could be demonstrated at 100 C at 1 atm; however, at 105 C moderate hydrostatic pressures favored the enzyme reaction, resulting in increased activity. The increased enzyme activity is explained on the basis of pressure counteracting the molecular volume increase which results from elevated temperature. Thermal denaturation studies at 90 C show inorganic pyrophosphatase to be more stable in the presence of cofactor than substrate, and indicate an enyzme-cofactor intermediate in the hydrolysis.