Deoxycytidylate deaminase. Purification and some properties of the enzyme isolated from human spleen

Deoxycytidylate deaminase (dCMP aminohydrolase, EC 3.5.4.12) from human spleen has been purified to apparent homogeneity. The native M sub(r) of the enzyme is 109,500 and the Stokes radius is 43 A as determined by gel filtration. The subunit M) sub(r) =, 53,000 as determined by sodium dodecyl sulfate-gel electrophoresis, suggesting that the enzyme is a dimer in its native state. Human spleen deoxycytidylate deaminase has a broad pH optimum between 6.5 and 7.3. With isoelectric focusing, the enzyme demonstrated a single form with an isoelectric point of 5.10. Studies of the kinetic behavior of the purified enzyme showed a sigmoidal initial velocity versus) substrate concentration curve and highly specific regulaton by allosteric effectors dCTP and TTP.