Inhibition of deoxynucleotide-polymerizing enzyme activities of human cells and of simian sarcoma virus by heparin.

Heparin inhibited the activities of: (a) reverse transcriptase from simian sarcoma virus; (b) DMA polymerases a, (i, and y from phytohemagglutinin-stimulated normal hu man lymphocytes, human leukemic lymphoblasts, and Molt-4 cells which are of acute lymphoblastic leukemia origin; and (c) terminal deoxynucleotidyl transferase from the two latter cell types. A 10-fold excess of enzyme overcame heparin inhibition of DNA polymerase a, ß,and y activities but not of simian sarcoma virus reverse transcriptase or terminal deoxynucleotidyl transferase activi ties. Heparin inhibition of all enzyme activities examined was partially surmounted by additional template primer or initiator, but additional deoxyribonucleoside S'-triphosphate, bovine serum albumin, or divalent cation had virtually no effect on heparin inhibition. The degree of inhibition of each enzyme by heparin was independent of time. Furthermore, addition of heparin to assay mixtures after the start of a reaction immediately inhibited each enzyme activity. Also, each enzyme was bound to a heparin-Sepharose 4B chromatography column and was eluted between 0.2 and 0.4 M NaCI. DMA polymerases a and y from the cellular soluble fraction and terminal deoxynucleotidyl transferase and DMA polymerases ß and y from the chromatin fraction were purified 9.6-, 71.2-, 3.2-, 2.3-, and 3.3-fold, respectively, by the above chromatography procedure. These results indicate that heparin inhibits all the enzyme activities studied by reversibly binding to each enzyme, thereby interfering with the interaction of template primer or initiator with enzyme.