Hydrolytic and Transferase Activities of Invertases from Physiological Races of Phytophthora Parasitica Var. Nicotianae

SUMMARY

Race 3 of Phytophthora parasitica var. nicotianae, the tobacco blackshank fungus, utilizes sucrose less readily than races 0 and 1 of this pathogen. Races 0 and 1 produce kestoses (fructosylsucrose) from sucrose but race 3 does not. Invertases commonly possess both hydrolytic and transferase (transfructosylation) functions. Mycelia from races 0 and 1 contained more invertase (based on hydrolytic activity per g of wet mycelia) than did mycelia from race 3. However, this difference did not explain lack of transferase activity in race 3 since invertases (both crude homogenates of mycelia and ammonium sulfate fractions) of races 0 and 1 diluted to 200-fold less than that found in race 3 still exhibited the transferase function. Data show both qualitative and quantitative differences in hydrolytic and transferase activities of invertase from three physiologic races of P. parasitica var. nicotianae.