Two intracellular β-glucosidases, designated P-I and P-II,
found in Aspergillus nidulans. While both enzymes were subject
carbon catabolite repression, they exhibited different degrees of repression.
P-I biosynthesis was repressed only by a strongly
repressing carbon source such as glucose. By contrast, P-II biosynthesis
repressed by even weakly repressing carbon sources
such as acetate or lactose. Repression of both was relieved in the
mutant strain, except for the strong repression of P-II
biosynthesis which was still repressed by glucose. Thus P-II biosynthesis
seems to be more sensitive to carbon catabolite repression than P-I.