While working on #694, I noticed a large number of transport reactions that transport (d)NTPs and (d)NDPs between the cytosol and mitochondria that are associated with SLC25A19 (ENSG00000125454). There is a warning at the top of the Uniprot page for SLC25A19 that says that, while it was initially claimed to be a mitochondrial nucleotide transporter, it was eventually shown to only be capable of transporting thiamine diphosphate.
All but 2 of the 56 reactions currently associated with SLC25A19 transport (d)NTPs and (d)NDPs between the cytosol and mitochondria, and I believe they should all be removed, since other existing reactions and the new ones proposed in #694 will ensure that all (d)NTPs and (d)NDPs can still move between the [c] and [m] compartments.
The two reactions that don’t involve nucleotides are MAR04933: AKG [e] + Na+ [e] ⇒ AKG [c] + Na+ [c] and MAR05047: Pi [l] ⇒ Pi [c]. MAR04933 is nearly identical to MAR05992, which uses 3 sodium ions instead of 1 and is associated with SCL13A3, which is actually known to catalyze that reaction according to Uniprot, so I think MAR04933 should be removed. MAR05047 appears to be the only way for inorganic phosphate to move from the lysosome to the cytosol, so I think it should be kept but have SLC25A19 removed from its GPR. As far as I can tell, people have known that phosphate is exported from human lysosomes since at least 1991 (source), but never determined which protein is responsible — this paper from 2021 cited that 1991 paper and no others when it mentioned lysosomal phosphate transport.
Proposed Changes
While working on #694, I noticed a large number of transport reactions that transport (d)NTPs and (d)NDPs between the cytosol and mitochondria that are associated with SLC25A19 (
ENSG00000125454). There is a warning at the top of the Uniprot page for SLC25A19 that says that, while it was initially claimed to be a mitochondrial nucleotide transporter, it was eventually shown to only be capable of transporting thiamine diphosphate.All but 2 of the 56 reactions currently associated with SLC25A19 transport (d)NTPs and (d)NDPs between the cytosol and mitochondria, and I believe they should all be removed, since other existing reactions and the new ones proposed in #694 will ensure that all (d)NTPs and (d)NDPs can still move between the [c] and [m] compartments.
The two reactions that don’t involve nucleotides are
MAR04933: AKG [e] + Na+ [e] ⇒ AKG [c] + Na+ [c]andMAR05047: Pi [l] ⇒ Pi [c].MAR04933is nearly identical toMAR05992, which uses 3 sodium ions instead of 1 and is associated with SCL13A3, which is actually known to catalyze that reaction according to Uniprot, so I thinkMAR04933should be removed.MAR05047appears to be the only way for inorganic phosphate to move from the lysosome to the cytosol, so I think it should be kept but have SLC25A19 removed from its GPR. As far as I can tell, people have known that phosphate is exported from human lysosomes since at least 1991 (source), but never determined which protein is responsible — this paper from 2021 cited that 1991 paper and no others when it mentioned lysosomal phosphate transport.Proposed Changes
ENSG00000125454from GPR ofMAR05047MAR04933for being a duplicate ofMAR05992