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Spermidine Biosynthesis in the Human Intestine: The Role of Commensal Bacteria

18 Décembre 2025, 13:09pm

Publié par Box News

Spermidine Biosynthesis in the Human Intestine: The Role of Commensal Bacteria

Spermidine is a small organic molecule called a polyamine that cells use for growth, repair and many basic processes. In the human gut it comes from three places: the food we eat, the cells of our own body, and the bacteria that live in the intestine. A range of common gut microbes are able to make spermidine themselves, so the community of bacteria in the intestine helps determine how much of this molecule is present in the gut lumen. (Frontiers)

Not every microbe uses the same recipe. Classic laboratory and animal studies have shown that bacteria from genera often found in the human gut — for example Bacteroides and Fusobacterium — can produce putrescine and spermidine when given appropriate food substrates in the gut, and other groups such as Escherichia, Lactobacillus and Bifidobacterium are also associated with polyamine production in different studies. Those are examples rather than an exhaustive list: many species across different bacterial families carry the enzymes needed to make these molecules, and which species are important can vary with diet and the individual’s microbiome composition. (MDPI)

Biochemically, most bacterial spermidine production follows a two-step idea: bacteria first make putrescine from amino acids (arginine or ornithine) and then convert putrescine into spermidine. Putrescine can be generated by enzymes called decarboxylases (ornithine decarboxylase or arginine decarboxylase, depending on the route). To make spermidine a second set of enzymes is used: S-adenosylmethionine decarboxylase provides an activated propylamine donor and spermidine synthase (often called SpeE) transfers that propylamine onto putrescine to form spermidine. These enzymatic steps are well described in reviews of bacterial polyamine metabolism and explain why many different gut bacteria can contribute to the pool of spermidine. (MDPI)

Some bacteria use alternative chemical routes. A notable example is Campylobacter jejuni, which lacks the standard SpeD/SpeE pair yet still makes spermidine by a different “carboxyspermidine” style pathway. More recently, researchers have discovered further alternative bacterial pathways (for example a carboxy-aminopropylagmatine route reported in 2023) that broaden the kinds of microbes we know can make spermidine. Those alternative pathways matter because they show that spermidine production is widespread and biochemically diverse across the microbiome, not confined to a single canonical pathway. (immunenetwork.org)

Finally, production in the gut is dynamic: what bacteria make depends on what substrates are available (the diet, especially amino acids and fermentable fibers), the presence of particular bacterial strains, and interactions between microbes and host cells that can both supply and take up intermediates. Intervention studies show that adding certain probiotics or dietary components can change microbiome-derived spermidine levels, illustrating that bacterial spermidine output can be modified by what we eat or by changing the resident microbes. In short, multiple gut bacterial groups can produce spermidine through one of several biochemical routes, and diet plus microbial ecology determines how much of that bacterial spermidine ends up in the intestine. (PMC)

(Source : ChatGPT)

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