XVI International Botanical Congess

We developed a nonisotopic method to assay poly(ADP-ribose) polymerase (PARP) activity in plants through determining nicotinamide produced by enzymatic reaction by linear sweeping polarographic method. The detection limit of nicotinamide was 0.03¦ÌM, the calibration graph was linear up to 5¦ÌM(r=0.999). The recovery ranged from 92% to 98% and the relative standard deviations were less than 6.6%. Interference existing in the mixture after enzymatic reaction had been removed by simple pretreatment. The results showed the Km value of PARP in maize was 59 and the optimum pH for PARP was 8.5. When tobacco cells were stressed by 100-200 mM NaCl, the PARP activity increased significantly, while at high concentrations (400, 1000 mM), it was lower than the control. PARP activity in etiolated maize was higher than that in light-grown maize.