As stated in an earlier post, the most prominent reported smell type for TMAU2 patients was the fecal smell type.
But not only TMAU positive patients reported such a type of smell, another body odor sufferer type do show the same fecal body odor pattern. Interestingly nearly all of those non TMAU patients report having Irritable Bowel Syndrom (IBS) as well.
We took a closer look into the combined bacterial and human metabolism.
The central chemical compound involved in the fecal smell seems to be indole.
Indole is produced within the bacterial metabolism as a precursor of tryptophan.
As major source the bacteria use glycolysis based on sugar, carbohydrates, ...
To let the bacteria produce too much indole we found certain criteria:
- Tryptophan absorption of the intestinal cells is lower than the serine and glycine absorption
- Histidine malabsorption is present
- Tyrosine malabsorption is present
Why do TMAU2 patients now show a fecal smell, don't they have a choline and betaine malabsorption?
Yes they have but it seems that there are several different enzyme defects in the choline degradation pathway leading to such a choline malabsorption.
Some of those defects do also have an indirect impact on the histidine degradation over the histamine n-methyltransferase (HNMT) enzyme which leads to an histidine malabsorption also.
Additionally the tryptophan and tyrosine degradation is further cuppled to the histidine degeadation and as a result they show a tryptophan and tyrosine malabsorption also.
So for people being TMAU negative and having a fecal body odor type it is very likely to have an enzyme defect in the histidine degradation pathway over the HNMT enzyme.