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bioRxiv · 10.64898/2026.06.22.733665

A PLP-Dependent Decarboxylative Mannich Reaction Initiates Construction of the Nonpeptidic Scaffold of Kaitocephalin

Noguchi, T.·Maeno, Y.·Shin-ya, K.·Kuzuyama, T.
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Abstract

Kaitocephalin (KCP) is a fungal neuroactive natural product bearing a peptide-like yet nonpeptidic amino acid-derived scaffold in which amino acid-like units are connected by C-C bonds rather than peptide bonds. The enzymatic construction of this unusual scaffold has remained unresolved. Here, we identify KpbH as a PLP-dependent enzyme that couples pyrroline-5-carboxylate, generated from L-ornithine, with L-aspartate to form (2S,5R)-5-((S)-2-amino-2-carboxyethyl)pyrrolidine-2-carboxylic acid (ACPCA), which corresponds to the nonpeptidic Ala-Pro substructure of KCP. D2O-labeling experiments showed enzyme-controlled, solvent-derived deuterium incorporation at C7 of ACPCA, supporting a decarboxylative Mannich-type mechanism. Feeding of a deuterium-enriched ACPCA-containing reaction mixture to the KCP-producing fungus Eupenicillium shearii resulted in deuterium incorporation into KCP, linking ACPCA to KCP biosynthesis. These results identify KpbH as the first native PLP-dependent enzyme that catalyzes an L-aspartate-dependent decarboxylative Mannich-type C-C bond-forming reaction and reveal a biosynthetic strategy for constructing a noncanonical amino acid-like C-C bond scaffold. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/733665v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@6578eforg.highwire.dtl.DTLVardef@1e6d1b0org.highwire.dtl.DTLVardef@d0881forg.highwire.dtl.DTLVardef@98d3a5_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Noguchi, T., Maeno, Y., Shin-ya, K., Kuzuyama, T.. 2026-06-23. A PLP-Dependent Decarboxylative Mannich Reaction Initiates Construction of the Nonpeptidic Scaffold of Kaitocephalin. https://doi.org/10.64898/2026.06.22.733665

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