Synthesis of malformin by an enzyme preparation from Aspergillus niger

Area of Science:

• Biochemistry
• Microbiology
• Enzymology

Background:

• Malformin is a cyclic pentapeptide produced by Aspergillus niger.
• The biosynthesis pathway of malformin was not fully understood.

Purpose of the Study:

• To investigate the enzymatic synthesis of malformin.
• To elucidate the role of amino acids and cofactors in malformin production.

Main Methods:

• Utilized a cell-free enzyme preparation from Aspergillus niger.
• Employed labeled amino acids to track incorporation into malformin.
• Assessed the effects of cofactors (ATP, K+, Mg++) and pH on the synthesis.

Main Results:

• An enzyme fraction synthesized malformin from component amino acids.
• Adenosine triphosphate, K+, and Mg++ stimulated the synthesis, optimal at pH 8.5.
• Inhibitors of protein synthesis did not affect malformin production.
• Evidence suggests cysteine incorporation followed by disulfide bridge formation.
• Both L- and D-isomers of cysteine and leucine were utilized, indicating potential D-isomer formation from L-isomers.

Conclusions:

• Aspergillus niger possesses an enzyme system for direct malformin synthesis.
• The pathway differs from canonical protein synthesis, involving post-translational disulfide bond formation.
• The system can interconvert L-amino acids to D-amino acids during synthesis.