Evidence for a Second ‘Structural’ Locus determining Human Phosphoglucomutase

Abstract

AT least seven isoenzyme components¹ of human phosphoglucomutase (PGM) can be distinguished electrophoretically (a–g, Fig. 1). Individual differences occur in the pattern of components present, and three commonly occurring phenotypes have been recognized (PGM 1, PGM 2–1 and PGM 2). They differ in the distribution of components a, b, c and d. Components a and c are present in PGM 1 and PGM 2–1, while components b and d are present in PGM 2–1 and PGM 2. The genetical evidence indicates that these phenotypic differences are due to a pair of autosomal alleles (PGM¹ and PGM²). Evidently a structural locus is involved, and it seems likely that one of these alleles determines the formation of a polypeptide common to a and c, while the other allele determines the formation of an alternative polypeptide common to b and d. The three phenotypes do not differ from one another in the occurrence of components e, f and g. This suggests that at least one other ‘structural’ locus is involved in the determination of these latter components.