Pyruvate kinase isozyme (PK-Greenville) with defective allosteric activation by fructose-1,6-diphosphate: the role of F-1,6-P modulation in normal erythrocyte metabolism

A child with chronic hemolytic anemia since birth was found to have erythrocyte pyruvate kinase (PK) in a highly unusual form relative to other mutant isozymes when characterized by International Committee for Standardization in Hematology criteria. Most properties of the partially purified isozyme (designated PK-Greenville) were altered minimally, if at all, except for nearly total insensitivity to allosteric activation by fructose-1,6-diphosphate (F-1,6-P). One parent appeared to be heterozygous for a null gene and the other for an allele governing production of the mutant isozyme. Apparent restriction of the molecular defect to ineffective activation kinetics suggests that the F- 1,6-P binding site on erythrocyte PK is functionally as well as physically allosteric. The magnitude of the metabolic block at the PK step and the clinical severity indicate that allosteric modulation by F- 1,6-P is a crucial property of PK in normal erythrocyte metabolism.