Complete Biosynthetic Pathway of the Phosphonate Phosphonothrixin: Two Distinct Thiamine Diphosphate-Dependent Enzymes Divide the Work to Form a C–C Bond

• Published in: Journal of the American Chemical Society Vol. 144; no. 37; pp. 16715 - 16719
• Main Authors: Zhu, Yuxun, Shiraishi, Taro, Lin, Jianwen, Inaba, Keito, Ito, Atsuro, Ogura, Yusuke, Nishiyama, Makoto, Kuzuyama, Tomohisa
• Format: Journal Article
• Language: English
• Published: American Chemical Society 21.09.2022
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.2c06546

Phosphonates often exhibit biological activities by mimicking the phosphates and carboxylates of biological molecules. The phosphonate phosphonothrixin (PTX), produced by the soil-dwelling bacterium Saccharothrix sp. ST-888, exhibits herbicidal activity. In this study, we propose a complete biosynthetic pathway for PTX by reconstituting its biosynthesis in vitro. Our intensive analysis demonstrated that two dehydrogenases together reduce phosphonopyruvate (PnPy) to 2-hydroxy-3-phosphonopropanoic acid (HPPA) to accelerate the thermodynamically unfavorable rearrangement of phosphoenolpyruvate (PEP) to PnPy. The next four enzymes convert HPPA to (3-hydroxy-2-oxopropyl)­phosphonic acid (HOPA). In the final stage of PTX biosynthesis, the “split-gene” transketolase homologue, PtxB5/6, catalyzes the transfer of a two-carbon unit attached to the thiamine diphosphate (TPP) cofactor (provided by the acetohydroxyacid synthase homologue, PtxB7) to HOPA to produce PTX. This study reveals a unique C–C bond formation in which two distinct TPP-dependent enzymes, PtxB5/6 and PtxB7, divide the work to transfer an acetyl group, highlighting an unprecedented biosynthetic strategy for natural products.