Covalent coupling of calf brain prolidase.

Calf brain prolidase covalently bound to CNBr-Sepharose 4B, retained about 32% of the activity of the uncoupled enzyme. The free enzyme showed slightly greater stability than the bound preparation when stored at 20 degrees C or at 0 degrees C. However, in either case the free and bound enzymes were more stable at the lower temperature. Greater thermal stability was shown by the free enzyme than by the bound preparation over a temperature range of 25 degrees C-60 degrees C. The free and bound prolidase, with and without Mn+2, had maximal activity at pH 4.0. Although the bound enzyme showed a single maximum, the free preparation exhibited three pH maxima of 4.0, 9.0, and 6.5, in decreasing order of activity. The ions Ag+, Cu+, Hg+2, and Zn+2 were strongly inhibitory on the free enzyme, whereas inhibition of the bound enzyme, with the exception of Zn+2 , was less. Unlike the coupled enzyme, a stimulatory effect was obtained on the free preparation with Co+3, Mg+2, and Mn+2. Various other compounds were studied and their effects were noted.