Secreted invertase activity ofnpamutants. The ability of mutants to secrete the enzyme invertase at the non-permissive temperature (34°) in response to low glucose was determined. Absolute values were normalized to the wild-type control assayed at the same time and plotted as % wild-type activity. A. The average % activity and standard deviation of npa mutants in the secretory pathway. B. Invertase activity from 96 of the remaining 100 uncharacterized npa mutants was assayed. In strains assayed multiple times (15/96), the average activity from independent assays is presented.