Regulation of α-aminoadipate reductase from Penicillium chrysogenum in relation to the flux from α-aminoadipate into penicillin biosynthesis

Abstract

The activity and regulation of alpha-aminoadipate reductase in three Penicillium chrysogenum strains (Q176, D6/1014/A, and P2), producing different amounts of penicillin, were studied. The enzyme exhibited decreasing affinity for alpha-aminoadipate with increasing capacity of the respective strain to produce penicillin. The enzyme from all three strains was inhibited by L-lysine, and the enzyme from the lowest producer, Q176, was least sensitive. Between pH 7.5 and 6.5, inhibition of alpha-aminoadipate reductase by L-lysine was pH dependent, being more pronounced at lower pH. The highest producer strain, P2, displayed the lowest alpha-aminoadipate reductase activity at pH 7.0. In Q176, the addition of 0.5-1 mM of exogenous lysine stimulated penicillin formation, whereas the same concentration was ineffective or inhibitory with strains D6/1014/A and P2. The addition of higher (up to 5 mM) lysine concentrations inhibited penicillin production in all three strains. In mutants of P. chrysogenum D6/1014/A, selected for resistance to 20 mM alpha-aminoadipate, highest penicillin production was observed in those strains whose alpha-aminoadipate reductase was most strongly inhibited by L-lysine. The results support the conclusion that the in vivo activity of alpha-aminoadipate reductase from superior penicillin producer strains of P. chrysogenum is more strongly inhibited by lysine, and that this is related to their ability to accumulate increased amounts of alpha-aminoadipate, and hence penicillin.

Transcriptional upregulation of four genes of the lysine biosynthetic pathway by homocitrate accumulation in Penicillium chrysogenum: homocitrate as a sensor of lysine-pathway distress

“…In wild-type strains the a-aminoadipate pool is limiting for penicillin production (Hönlinger & Kubicek, 1989;Lu et al, 1992). A correlation between intracellular aaminoadipate concentration and penicillin production has been reported in P. chrysogenum strains with different penicillin production ability (Jaklitsch et al, 1986;Hijarrubia et al, 2002).…”

Domain Structure Characterization of the Multifunctional α-Aminoadipate Reductase from Penicillium chrysogenum by Limited Proteolysis

“…The strain used derives from P. chrysogenum Wis 54-1255, which shows partial lysine requirement in minimal medium and an improved penicillin production when compared with the wild type. 4 The relatively low affinity of ␣-AAR toward its substrate ␣-AA would lead to an increase in the ␣-AA intracellular levels, which favor the formation of the tripeptide ␦-L-(␣-aminoadipyl)-L-cysteinyl-D-valine, and hence penicillin formation (21). We have previously correlated high penicillin-producing strains with increased intracellular ␣-AA pools (15).…”

Control of Fluxes Towards Antibiotics and the Role of Primary Metabolism in Production of Antibiotics

“…Lysine also exerts feedback inhibition on the conversion of L-a-aminoadipic acid to d-adenyl-a-aminoadipate by L-a-aminoadipic acid reductase [68]. This inhibition is more pronounced in high-yielding strains of penicillin than in low-yielding strains [69]. Thus, high-yielding strains of P. chrysogenum, obtained by classical strain improvement, seem to have acquired mutations favouring a larger supply of L-aaminoadipic acid to the penicillin biosynthesis pathway.…”