ONTOGENY OF CHICK LIVER HEXOKINASE ISOZYMES

  • 1 January 1981
    • journal article
    • research article
    • Vol. 14  (4) , 331-341
Abstract
Glucose phosphorylating activities were measured in liver extracts from chicks at several developmental stages. Enzyme activity levels in supernates were low (.apprx. 0.16 units/g liver) from day 10 of egg incubation until day 17, at which time a transient increase to 0.5 units/g was observed. At hatching, the levels were again low (0.15 units/g) compared to adult levels (0.9 units/g). Particulate hexokinase activity was rather constant from day 10 to adulthood (.apprx. 0.3 units/g). Chromatography of liver supernates in DEAE-cellulose columns revealed the presence of 4 hexokinases in embryos up to day 15 of incubation. From that day onwards, the least retained form (hexokinase 4) was no longer found. The most retained form (hexokinase 1) disappeared at hatching, at which time a pattern consisting of hexokinases 2 and 3 was found to be very similar to the adult profile. The 4 isozymes were characterized as low Km glucose hexokinase of broad sugar specificities and MW of about 100,000. Particulate hexokinase activity of embryonic chick liver was composed of the same isozymes observed in cytosolic extracts. Incubation of particles with G-6-P or ATP failed to release hexokinase activity.