Hypoxanthine phosphoribosyltransferase: two-dimensional gels from normal and Lesch-Nyhan hemolyzates

Immunoprecipitated hypoxanthine phosphoribosyltransferase (HPRT) from hemolyzates displays two major spots after two-dimensional polyacrylamide gel electrophoresis. HeLa cells or human lymphoblasts display only a single HPRT spot located at the same position as the most basic of the hemolyzate HPRT spots. This suggests that the most basic spot is the form initially synthesized, and the more acidic hemolyzate HPRT spot (a pseudoisozyme) is probably derived from the first by an age-related modification (for example, deamidation). The HPRT pattern of the hemolyzate from a Lesch-Nyhan patient was shifted to a more basic isoelectric pH, implying the mutation of a structural gene.