Comparative inductive responses of two beta-galactosidases of Neurospora

The activities of the two beta-galactosidases of Neurospora increased in response to the presence of lactose or galactose. d-Xylose preferentially induced higher levels of activity in one of these enzymes. The initial period of the inductive response was examined in cultures transferred from noninducing to inducing media. Variations in the ratio of activities of these enzymes during this induction period indicate that their induction was not coordinate. The induction of the beta-galactosidases of Neurospora was less sensitive to low concentrations of inducers than was the induction of the beta-galactosidase of bacteria; the time lag of induction was greater in the eucaryotic organism, and the maximal induction of active enzyme was less than that observed in bacteria.