Mouse brain contains a high molecular weight nonfunctional protein with antigenic homology to dihydrofolate reductase.
The cytosol of brain tissue from mature BDF1 mice contains very little dihydrofolate reductase activity but it does contain a high molecular weight nonfunctional protein which cross-reacts in a radioimmunoassay for the active enzyme. Liver cytosol contains less of this high molecular weight cross-reacting protein and more of the functional dihydrofolate reductase. The cytosol from kidney contains very little of the high molecular weight cross-reacting protein, 95% of the immunoreactive proteins being the functional form of dihydrofolate reductase. The modification of dihydrofolate reductase into a nonfunctional form may be an intrinsic property of some cells and this finding could explain the variability in measuring the activity of this enzyme in brain tissue of mature animals.
D000818:Animals; D001923:Brain Chemistry; D003429:Cross Reactions; D003600:Cytosol / Q000032:analysis; D007526:Isoelectric Point; D007668:Kidney / Q000032:analysis; D008099:Liver / Q000032:analysis; D008727:Methotrexate / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000276:immunology*; D011863:Radioimmunoassay; D013762:Tetrahydrofolate Dehydrogenase / Q000276:immunology* / Q000378:metabolism
D009419:Nerve Tissue Proteins; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate