Interference by methionine on valine uptake in Acremonium chrysogenum

Area of Science:

• Microbial biosynthesis
• Antibiotic precursor synthesis
• Biochemistry

Background:

• Delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) is a critical intermediate in the biosynthesis of penicillin and cephalosporin antibiotics.
• Understanding the regulation of ACV synthesis is essential for optimizing antibiotic production.
• Amino acid metabolism plays a significant role in secondary metabolite production in microorganisms.

Purpose of the Study:

• To investigate the effect of methionine and its analog, norleucine, on the incorporation of L-[U-14C]valine into ACV.
• To elucidate the mechanism by which methionine and norleucine influence ACV biosynthesis in Acremonium chrysogenum.

Main Methods:

• Culturing Acremonium chrysogenum in the presence and absence of DL-methionine and DL-norleucine.
• Tracing the incorporation of radiolabeled L-[U-14C]valine into the ACV molecule using radioactive detection.
• Analyzing the impact of methionine and norleucine on valine transport into the microbial cells.

Main Results:

• The addition of DL-methionine to culture broths completely inhibited the formation of radioactive ACV.
• DL-Norleucine, a nonsulfur analog of methionine, also demonstrated an inhibitory effect on radioactive ACV synthesis, though to a lesser extent.
• The observed inhibition was attributed to the interference of methionine and norleucine with the transport of valine across the cell membrane.

Conclusions:

• Methionine and norleucine significantly impact the biosynthesis of ACV, a key penicillin and cephalosporin precursor.
• The inhibitory mechanism involves the disruption of essential amino acid (valine) uptake by the producing microorganism.
• These findings provide insights into the metabolic regulation of antibiotic precursor synthesis and potential strategies for yield improvement.