Uptake and metabolism of α-aminoadipic acid by Penicillium chrysogenum wis 54-1255

Abstract

The uptake of 1-¹⁴C-dl-α-aminoadipate in resting mycelium of Penicillium chrysogenum Wis 54-1255 and its metabolism during benzylpenicillin formation were studied. The pH optimum for uptake at 25°C was 6.4. Over a range of concentrations from 0.01–1.0 mM, approximately 45% of 1-¹⁴C-dl-α-aminoadipate was taken up by carbon-starved mycelium. ¹⁴CO₂ was formed at a low rate, and the total formed amounted to only 1–3% of the 1-¹⁴C-dl-α-aminoadipate supplied. The intracellular pool of α-aminoadipate appears to be expandable, depending on the concentration of α-aminoadipate in the medium. The rate of penicillin synthesis depended on the intracellular concentration of α-aminoadipate. Penicillin biosynthesis achieved half of the maximum rate at an intracellular concentration of 0.06 nmol α-aminoadipate/mg dry cell weight. This low concentration, the result of adding 0.01 mM dl-α-aminoadipate to the medium, was sufficient to reverse the inhibition of penicillin biosynthesis caused by 10 mM extracellular l-lysine. Aminoadipate appears to be recycled during penicillin formation. Labeled α-ketoadipate was formed from α-aminoadipate to the extent of about 25%.