Phileucin - A Cyclic Dipeptide Similar to Phevalin (Aureusimine B) from Streptomyces coelicolor M1146

Area of Science:

• Marine microbiology
• Natural product biosynthesis
• Enzymology

Background:

• Marine myxobacteria are a source of novel bioactive compounds.
• Polyketide synthases (PKS) are key enzymes in natural product biosynthesis.
• Type III PKS enzymes have diverse catalytic capabilities.

Purpose of the Study:

• To investigate the biosynthetic potential of a type III polyketide synthase (PKSIII) from Enhygromyxa salina SWB007.
• To characterize the novel compound produced by heterologous expression of the PKSIII gene.
• To evaluate the protease inhibiting activity of the novel compound.

Main Methods:

• Heterologous expression of the putative PKSIII gene from E. salina SWB007 in Streptomyces coelicolor MI 146.
• Isolation and structural elucidation of the accumulated metabolite.
• Biochemical assays to determine protease inhibiting activity against human cathepsin L, human leukocyte elastase, bovine trypsin, and bovine chymotrypsin.

Main Results:

• Overexpression of the E. salina PKSIII resulted in the production of a novel monoketopiperazine, named phileucin.
• Phileucin is composed of phenylalanine and isoleucine residues.
• Phileucin exhibits high structural similarity to phevalin (aureusimine B).
• Phileucin demonstrated no significant protease inhibiting activity against the tested enzymes.

Conclusions:

• The marine PKSIII from Enhygromyxa salina SWB007 can produce a novel monoketopiperazine, phileucin.
• Phileucin represents a new structural class of compounds derived from this PKSIII.
• Despite structural similarity to phevalin, phileucin lacks protease inhibiting activity, suggesting distinct biological functions or structure-activity relationships.