Vaginal flora: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Vaginal flora composition: which stations follow one another, which enzymes carry out each step and which cofactors they use. Every statement has a source. The page describes general textbook knowledge and says nothing about any individual person.

In brief

The vaginal flora is the community of microorganisms in the vagina, often dominated by lactobacilli. These break down sugars from glycogen into lactic acid; other organisms such as Gardnerella or the protist Trichomonas can also occur.

The pathway step by step

1. Estrogen → Glycogen Glycogen is a branched chain of glucose. It is released when cells of the lining are shed. Source 1
2. Glycogen → Maltose and glucose α-amylase The body's own α-amylase in the mucus breaks glycogen down into smaller sugars. Only in this form can bacteria use it. Source 2
3. Sugar in the cell → Lactic acid Lactate dehydrogenase · NADH This breakdown produces lactic acid, in the L or the D form depending on the species. The bacteria release it into the mucus. Source 1
4. Lactic acid → Acidic milieu Lactic acid keeps the mucus acidic. In this milieu many other bacterial species grow more slowly, while lactobacilli cope well with it. Source 1
5. Mucins in the mucus → Free sialic acid Sialidase Gardnerella produces a sialidase. The enzyme detaches sialic acids from the sugar chains; the bacterium absorbs and uses them. Source 4
6. Trichomonas vaginalis → Attachment to the cell Adhesins When the organism meets cells of the lining, it changes shape from oval to flat and attaches with surface proteins. Among other things, it feeds on bacteria of the flora. Source 5

Cofactors in this pathway

• NAD⁺ — Coenzyme of lactate dehydrogenase, which lactobacilli use to form lactic acid Source 1
• Calcium — Bound ion of alpha-amylase, which breaks glycogen down into smaller sugars Source 6, 2In the ORY catalogue as a laboratory value: Calcium (intrazellulär)
• Chloride — Bound ion near the active site of alpha-amylase Source 6
• Iron — Part of the iron-sulphur proteins in the hydrogenosomes of Trichomonas Source 7

Sources

1. Amabebe E, Anumba DOC. The Vaginal Microenvironment: The Physiologic Role of Lactobacilli. Front Med (Lausanne) 2018 · PubMed 29951482
2. Spear GT, French AL, Gilbert D et al. Human α-amylase present in lower-genital-tract mucosal fluid processes glycogen to support vaginal colonization by Lactobacillus. J Infect Dis 2014 · PubMed 24737800
3. Ravel J, Gajer P, Abdo Z et al. Vaginal microbiome of reproductive-age women. Proc Natl Acad Sci U S A 2011 · PubMed 20534435
4. Lewis WG, Robinson LS, Gilbert NM et al. Degradation, foraging, and depletion of mucus sialoglycans by the vagina-adapted Actinobacterium Gardnerella vaginalis. J Biol Chem 2013 · PubMed 23479734
5. Leitsch D. Recent advances in the molecular biology of the protist parasite Trichomonas vaginalis. Fac Rev 2021 · PubMed 33718943
6. Brayer GD, Luo Y, Withers SG. The structure of human pancreatic alpha-amylase at 1.8 A resolution and comparisons with related enzymes. Protein Sci 1995 · PubMed 8528071
7. Tachezy J, Makki A, Hrdý I. The hydrogenosome of Trichomonas vaginalis. J Eukaryot Microbiol 2022 · PubMed 35567536

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert review pending. The biological process is described; the aromatogram is intentionally not shown.
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