Purification and characterization of phosphoglucose isomerase allozymes from Daphnia magna

Phosphoglucose isomerase (PGL EC 5.3.1.9) is polymorphic in many populations. Frequently, it has been shown that naturally occurring allozymes exhibit strong deviations form Hardy-Weinberg expectations, suggesting fitness relevant mutations. To investigate the nature of this allozymic variation, PGI was purified from Daphnia magna to high purity yielding a specific activity of 135.2 U/mg. The kinetic parameters of the allozymes were characterized depending upon ionic strength, pH and viscosity. The half-saturation constants of the allozymes were all equal, while the specific activity of the PGI from heterozygotes was consistently higher than the PGI of the homozygotes independent of pH, ionic strength and viscosity of the solution. (C) 2001 Societe francaise de biochimie et biologie moleculaire/Editions scientifiques ct medicales Elsevier SAS. All rights reserved.