Transglutaminase activity in normal and transformed cells.

Transglutaminase activity was determined in normal and transformed paired cell systems. Reduced enzyme activity was found in virus-transformed human and hamster cells and in chemically transformed mouse cells relative to normal counterparts. Most of the enzyme activity was localized in the particulate fraction sedimenting at 105,000 X g. Enzyme activity was highest when normal cell populations were in an essentially nonmitotic state. Protein capable of incorporating putrescine was present in normal and transformed human cells, although the rate of incorporation was lower in the latter. The putrescine acceptor in the normal cell paralleled enzyme activity and enzyme distribution. Trypsin (5 microng/ml) treatment of the normal cell resulted in a 3-fold increase in enzyme activity, which occurred independently of protein synthesis.