Study of hepatic tyrosine aminotransferase from Schistosoma-infected mice

In the current study, tyrosine aminotransferase (TAT) as a target enzyme was purified from the liver of control and Schistosoma-infected mice that was subjected to catalytic investigation. The purified enzyme has a single band on SDS-PAGE with a molecular mass of almost 100 KD from control and infected mice. The kinetic studies of hepatic TAT towards its substrates showed no change in K_m, whereas V_max value was increased from 2.3 to 2.9 fold in the enzyme isolated from Schistsoma- infected mice. In addition, the K_cat/ K_m ratio displayed a higher value for the enzyme from infected mice, indicating that it is more efficient and specific. On the other hand, the in vitro effect of praziquantel showed a slight activation of hepatic TAT in both control and infected mice, whereas mirazid (MZD) has an inhibitory effect in a concentration-dependent manner. The response of TAT from infected mice towards MZD inhibition is less than that from controls. These data suggest that there is a change in the catalytic properties of hepatic TAT in schistosomiasis and the in vitro effect of the schistosomicidal drugs appears to have inductive or inhibitory effect.