Allelic expression in intergeneric fox hybrids (Alopex lagopus x Vulpes vulpes). II. Erythrocyte glucose-6-phosphate dehydrogenase in Artic and silver foxes: purification and properties.

The functional properties of purified glucose-6-phosphate dehydrogenase (G6PD) from the erythrocytes of Artic foxes (Alopex lagopus) and silver foxes (Vulpes vulpes) were investigated. It was found that pH optima for G6P D range from 8.15 to 8.25 in Arctic foxes and from 10.2 to 10.4 in silver foxes. For G6P, the estimated Km values were 74 X 10(-6) M (at pH 8.2) and 166 X 10(-6) M (at pH 10.2) in Artic foxes and 58 X 10(-6) M (at pH 10.2) and 40 X 10(-6) M (at pH 8.2) in silver foxes. The Km values for NADP were estimated as 62 X 10(-6) M (at pH 8.2) and 86 X 10(-6) M (at pH 10.2) in the Artic foxes and 15 X 10(-6) M (at pH 10.2) and 12 X 10(-6) M (at pH 8.2) in the silver foxes. It was found that Mg2+ ions exert a significant activating effect on G6P D in the Arctic fox and do not affect appreciably its activity in the silver fox. The experimental data indicate that slight differences in the electrophoretic mobility of G6P D are associated with considerable functional differences in this enzyme between the two fox species.