Further genetic heterogeneity of human red cell phosphoglucomutase-1: a non-electrophoretic polymorphism

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Abstract
The electrophoretic patterns of human red cell phosphoglucomutase (PGM) were determined by standard starch-gel electrophoresis on two aliquots of haemolysate, one of which was previously heat-treated. Samples from 67 families and 417 unrelated healthy subjects were examined. Heat denaturation studies combined with electrophoresis showed a greater heterogeneity of phosphoglucomutase-1 (PGM1) isozymes than that revealed by electrophoresis alone. Both PGM11 and the PGM21 isozymes turned out to be either heat-resistant (tr) or heat-sensitive (ts) and this new phenotypic property segregated along with the electrophoretic allele with which it was originally associated. Comparison of red cell PGM1 patterns of 217 PGM21-1 heterozygous individuals, analysed both as described in this paper and by acid starch-gel electrophoresis, which also distinguishes two common PGM11 (PGM1S1 and PGM1f1) and two common PGM12 (PGM2S1 and PGM2F1) allelic products, has shown that the two sets of four alleles do not coincide. Thus eight different PGM1 alleles were identified. The PGM1Str1, PGM1Sts1, PGM1Ftr1, PGM1FTSts1, PGM2Str1, PGM2Sts1, PGM2Ftr1 and PGM2Fts1 gene frequencies were estimated as 0 . 523, 0 . 066, 0 . 099, 0 . 029, 0 . 224, 0 . 012, 0 . 043, 0 . 004, respectively. Three polymorphic sites are hypothesized within the PGM1 structural gene and the observed frequencies of the eight alleles discussed in terms of 'disequilibrium' among these sites. This is the second example of a human enzyme isoelectrophoretic polymorphism revealed by research specifically aimed at detecting electrophoretically cryptic genetic variations. The technique used in this study appears to offer a reliable means of detecting isoelectrophoretic variants for proteins already known to be electrophoretically polymorphic.