Hi everybody,
I am wondering whether anyone is aware about the intracellular levels (molarity) of guanine in normal, healthy cells. I would be particularly interested in the levels measured in murine lung epithelial cells, but any general information on guanine levels and respective publications would be very helpful as well!
Thank you!
Hi Benjamin,
I am not sure of the answer. I used to work with hypoxanthine-guanine phosphoriboysltransferases (HGPRT) from human and Plasmodium falciparum. I am writing what I know and this may/may not be useful in your case. Guanine is very insoluble in aqueous solutions and some strong acid or alkali is needed to solubilize it. My guess therefore is that, it is probably found in the low micromolar range in cells at best. (because the Km for both hypoxanthine and guanine is around 1-2uM for these enzymes) Hypoxanthine is the purine base that is generally found at higher concentrations (it is better soluble too) and used in salvage pathways. The guanine specificity is probably present in these enzymes to scavenge the low levels guanine. Guanine and xanthine at higher concentrations may be toxic to the cell too. The deficiency of HGPRT causes Lesch-Nyhan syndrome and Gout possibly due to the accumulation of uric acid crystals. Surprisingly, mice lacking this enzyme are normal.
Sorry I could not be more specific. I was waiting for someone to answer your question. Then realized may be either the literature is old or there is none. The malaria field should have some references on the levels of hypoxanthine in the red blood cells that the Plasmodium parasite uses. If time permits I will try to dig something out.
Good luck
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