Structural highlights
FunctionPublication Abstract from PubMedPolyamines are key signalling and substrate molecules that are made by all organisms. The polyamine known as spermidine is typically made by spermidine synthase, but in many bacterial species, including 70% of human gut microbes, carboxyspermidine decarboxylase (CASDC) performs the terminal step in the production of spermidine. An X-ray crystal structure of CASDC from the human gut microbe Clostridium leptum has been solved by molecular replacement at a resolution of 1.41 A. CASDC is a homodimer, with each monomer composed of two domains: a beta/alpha-barrel pyridoxal 5'-phosphate-binding domain that forms most of the active site and a beta-barrel domain that extends the dimeric interface and contributes to the active site of the opposing monomer. We performed a structural comparison of CASDC enzymes for 15 common genera within the human gut flora. This analysis reveals structural differences occurring in the beta6/beta7 loop that acts as a ;flap' covering the active site and in the alpha9/beta12 loop that is connected to the alpha9 helix which is thought to select substrates by their chain length. This structural analysis extends our understanding of a key enzyme in spermidine biosynthesis in many bacterial species. Structure of Clostridium leptum carboxyspermidine decarboxylase and comparison to homologs prevalent within the human gut microbiome.,Jones SJ, Bell DJ, McFarlane JS Acta Crystallogr F Struct Biol Commun. 2025 Mar 1. doi: , 10.1107/S2053230X25000482. PMID:39887002[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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