Deoxyribonuclease I in mammalian tissues. Specificity of inhibition by actin

Enzymes of the DNase I class, similar to bovine pancreatic DNase I with respect to molecular weight and ionic and pH requirements, were found in various tissues of the rat. Their analysis was facilitated by a method for detection of nucleases in crude extracts after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and subsequent renaturation of the enzymes. High levels of DNase I were found in digestive tissues, such as the parotid and submaxillary salivary glands and the lining of the small intestine., Appreciable levels were present in the lymph node, kidney, heart, prostate gland, and seminal vesicle. No activity was found in pancreatic extracts. However, under some conditions, tissues rich in proteases gave poor recovery of DNase I. Fourteen other tissues showed little or no DNase I. Inhibition of various DNase I enzymes by rabbit muscle actin was examined both in gels and in solution. Actin inhibited the bovine parotid DNase I as well as the bovine pancreatic enzyme, but actin did not inhibit any of the DNase I enzymes of the rat. This species specificity of actin inhibition makes it unlikely that the very strong association between monomeric actin and bovine DNase I is of general significance for cellular function.