Genetic evidence for a second asparaginase in Aspergillus nidulans.

The apnA1 mutation strongly reduces L-asparagine utilization in Aspergillus nidulans. The ahrA1 mutation, leading to loss of an L-asparaginase (Drainas et al., 1977), eliminates residual L-asparagine utilization in double mutant strains also carrying apnA1. This additivity suggests that A. nidulans, like Saccharomyces cerevisiae (Jones, 1977; Dunlop et al., 1978), has two L-asparaginases specified by apnA and Ahr A, respectively, apnA has been mapped to a position on the left arm of linkage group II, in the sequence adH--acrA--apnA--wA--methA--palcA--(centromere).