AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 6 740-R746, Copyright © 1985 by American Physiological Society
Properties of pig mature erythrocyte hexokinase
F. J. Kearse and E. Dixon
Previous studies have demonstrated the presence of two type III hexokinase
isozymes in pig mature erythrocytes. The prevalence of a specific isozyme
species is an age-dependent phenomenon. The mature erythrocyte of young
adult pigs (less than 6 mo old) possess an isozyme that has an apparent Km
for glucose that is lower than in adult pigs. The data in this report
suggest several basic differences between the two isozymes.
D-Mannoheptulose, a structural analogue of glucose, was observed to
differentially inhibit the isozymes. The young adult isozyme tended to be
heat sensitive when compared with adult isozymes. Carboxypeptidase B and
trypsin inhibited the activity of both isozymes, but the young adult
isozyme was most dramatically affected by carboxypeptidase B. When the two
isozymes were incubated in the presence of two sulfhydryl group inhibitors,
HgCl2 and 5,5'-dithiobis [2-nitrobenzoic acid] (DTNB), the young adult
isozyme exhibited the greater inhibition in the presence of DTNB. The data
suggest that the young adult isozyme exhibited pronounced differences in
activity when incubated in the presence of DTNB and carboxypeptidase B.
These two agents may be used as probes to further characterize the
properties of the two isozymes.
