Salt inhibition of nuclear histone acetyltransferase from calf thymus.

: Nuclear histone acetyltransferase isolated from calf thymus was found to be inhibited by numerous salts at millimolar concentrations. Salts made up of monovalent ions caused 50% decrease in enzymatic activity at an average concentration of 51 +/- 14 mM while the same degree of inhibition was achieved by divalent salts at 15 +/- 5 mM. At the same ionic strength in the range from 5 to 70 mM, the divalent salts were 14-31% more inhibitory than the salts of monovalent ions. Kinetic analysis showed that NaCl and (NH4)2SO4 inhibited the enzyme competitively against both acetyl-CoA and histones. The inhibition constants for NaCl against acetyl-CoA and histones are respectively 30 and 34 mM. That for (NH4)2SO4 are 8 and 12 mM respectively.