title: Elevated levels of erythrocyte hypoxanthine phosphoribosyltransferase associated with allelic variation of murine Hprt.
abstract: Murine stocks with wild-derived hypoxanthine phosphoribosyltransferase (HPRT) A alleles (Hprt a) have erythrocyte HPRT activity levels that are approximately 25-fold (Mus musculus castaneus) and 70-fold (Mus spretus) higher than those of laboratory strains of mice with the common Hprt b allele (Mus musculus: C3H/HeHa or C57B1/6). Since the purified HPRT A and B enzymes have substantially similar maximal specific activities (64 and 46 units/mg of protein, respectively), we infer that these HPRT activity levels closely approximate the relative levels of HPRT protein in these cells. Red blood cells of HPRT A and B mice have similar levels of adenine phosphoribosyltransferase activity (APRT; EC 2.4.2.7) and reticulocyte percentages, which suggests that the elevated levels of HPRT in erythrocytes of HPRT A mice are not secondary consequences of abnormal erythroid cell development. The HPRT activity levels in reticulocytes of HPRT B mice are approximately 35-fold higher than the levels in their erythrocytes and approach the HPRT activity levels in reticulocytes of HPRT A mice. Thus, the marked differences in the levels of HPRT protein in erythrocytes of HPRT A and B mice result from differences in the extent to which the HPRT A and B proteins are retained as reticulocytes mature to erythrocytes. The substantial and preferential loss of HPRT B activity from reticulocytes is paralleled by an equivalent loss of HPRT immunoreactive protein (i.e., CRM) from that cell, and we infer that the HPRT B protein is degraded or extruded as reticulocytes mature to erythrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000483:Alleles; D000818:Animals; D001921:Brain / Q000201:enzymology; D004912:Erythrocytes / Q000201:enzymology*; D005796:Genes; D014644:Genetic Variation; D007041:Hypoxanthine Phosphoribosyltransferase / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D013045:Species Specificity; D013154:Spleen / Q000201:enzymology; D014018:Tissue Distribution
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase