Pyruvate kinase activity and response to allosteric effectors in rat erythrocytes and reticulocytes fractionated by multiple partitioning in aqueous two-phase systems.

Specific activity of pyruvate kinase decreases as the age of rat erythrocytes increases in fractions obtained by counter-current distribution in dextran-polyethylene glycol biphasic systems; the enzyme is inhibited by ATP and activated by fructose-1,6-bisphosphate at low phosphoenol pyruvate concentrations. Specific activity does not change in fractions from greater than 95 per cent-rich reticulocytes (anaemic rats); the enzyme is inhibited by ATP but not activated by fructose-1,6-bisphosphate. These results can be explained on the basis of different pyruvate kinase isozymes and suggest that decrease in activity is not affecting regulatory properties during erythrocytes aging.

Bisphosphoglycerate mutase and pyruvate kinase activities during maturation of reticulocytes and ageing of erythrocytes.

An increase in bisphosphoglycerate mutase (BPGM) and a decrease in pyruvate kinase (PK), i.e. a decrease in PK/BPGM ratio, was observed in red cell populations from anemic rats containing 95% down to 3% reticulocytes in blood. Such a ratio has been used to study the fractionation of recticulocytes, according to their degree of maturation, after counter-current distribution of those cell populations in dextranpoly (ethylene glycol) two-phase systems. When applying this procedure to the fractionation according to age of erythrocytes from normal rats, the decrease of PK with cellular age was observed without a significant variation in BPGM activity.

Comparative kinetic behaviour and regulation by fructose-1,6-bisphosphate and ATP of pyruvate kinase from erythrocytes, reticulocytes and bone marrow cells.

1. Kinetic and regulatory properties of pyruvate kinase have been studied in haemolysates of erythrocytic populations from blood and bone marrow of rats. 2. Pyruvate kinase from normal rat erythrocytes showed sigmoidal kinetics vs phosphoenolpyruvate. In contrast, the enzyme from reticulocytes and erythroid-rich bone marrow cells behaved as hyperbolic. 3. The enzyme activities were always inhibited by ATP. Activation by fructose-1,6-bisphosphate was only observed in erythrocytes. 4. These kinetic differences suggest changes in pyruvate kinase isozymes in cells of the erythrocytic line of rats.

A comparative kinetics and regulatory study of pyruvate kinase from rat erythrocytes, reticulocytes and bone marrow cells.

The kinetics of pyruvate kinase (PK) at various phosphoenol pyruvate (PEP) concentrations, has been studied in cells of the erythrocytic line. The enzyme from erythrocytes shows positive cooperativity, it behaves as michaelian in reticulocytes and shows negative cooperativity in bone marrow cells. ATP exerts an inhibitory effect in all cases. The activator effect of fructose 1,6-bisphosphate (FBP) was found only in erythrocytes.