That the inhibition could be reversed
by L - α - aminoadipic acid led to the postulations [10] that (i) L - α - aminoadipic acid
was involved in penicillin biosynthesis although it did not end up in the fi nal
penicillin molecule, (ii) penicillin was derived from α - ketoglutarate and acetyl - CoA
via the fungal lysine biosynthetic pathway, and (iii) lysine inhibition of penicillin
biosynthesis was due to feedback inhibition by lysine of its own biosynthetic
pathway, thus limiting L - α - aminoadipic acid formation. Independently, Arnstein
and colleagues [11] detected the tripeptide δ - ( α - aminoadipyl) - cysteinylvaline ( ACV )
as an intracellular compound in P. chrysogenum .