Erythrocyte pyruvate kinase deficiency: A kinetic method for differentiation between heterozygosity and compound‐heterozygosity

Abstract

The goal of the present study was to search for criteria that allow one to distinguish between normal individuals and heterozygotes as well as compound heterozygotes for pyruvate kinase (PK) deficiency. As the residual activity of PK with heterozygotes was between 35% and 110% of the normal activity, it was necessary to find other methods to prove heterozygosity. The PK in the hemolysates of 23 patients suffering from PK deficiency, 36 paternal and maternal enzymes as well as the enzymes of five heterozygous and four normal siblings together with those of 20 normal individuals, were studied according to the recommendations of the International Committee for Standardization in Haematology. The following hematological and enzyme kinetic parameters can serve to identify heterozygotes for PK deficiency: 1) a slight reticulocytosis, 2) an up-to-twofold increase of the intracellular concentrations of glucose-6-phosphate in the erythrocyte, 3) a mixed cooperativity of the phosphoenolpyruvate (PEP)-binding process of PK, 4) a decreased nucleotide specificity with guanosine diphosphate and uridine diphosphate, and 5) a lowered affinity for adenosine diphosphate. The most significant criterium found with all heterozygotes was a mixed cooperativity of the PEP-binding process caused by the presence of a mixture of normal and mutant PK.

Prevalence of Erythrocyte Pyruvate Kinase Deficiency and Normal Values of Enzyme in a Turkish Population

“…Enzyme activity below 30% of normal activity was accepted as homozygous deficiency [8,10], There were no homozygous cases in our study group. Heterozygous defi ciency was detected in 7 males and 6 females.…”

Erythrocyte pyruvate kinase deficiency: Relations of residual enzyme activity, altered regulation of defective enzymes and concentrations of high‐energy phosphates with the severity of clinical manifestation3

“…Enzyme kinetic studies dealing with the regulatory properties of the defective PK were evaluated with a computer program developed in our laboratory (17).…”

“…Improved methods for cell separation, including a mathematical evaluation, allow one to determine the different enzyme activities in the erythrocyte and reticulocyte (16). Recently we could demonstrate that the degree of haemolysis in PK deficiency frequently is caused by alterations of the regulatory properties of the mutant enzyme (17). Additionally there were some reports describing a change of highenergy phosphate concentrations in the red blood cells and discussing their role in the perturbed energy metabolism in the case of PK deficiency (18,19).…”