S. Takegawa

Seven Pyruvate Kinase Variants Characterized by the ICSH Recommended Methods

Summary Seven new red‐cell pyruvate kinase (PK) variants were characterized by the methods recently recommended by the International Committee for Standardization in Haematology. The cases were all true homozygote as evidenced by consanguineous marriages of the parents; all are Japanese. These variants were designated as PK Tokyo, PK Nagasaki, PK Sapporo, PK Maebashi, PK Itabashi, PK Fukushima and PK Aizu, respectively. Low substrate affinity (high K0.5S for phosphoenolpyruvate) and thermal instability appear to play major roles in causing defective enzyme function, resulting in chronic haemolytic anaemia. Product inhibition of PK by ATP may also play an additional role in causing haemolysis in more than half the cases.

Change of pyruvate kinase isozymes from M2- to L-type during development of the red cell.

Summary. The relationship between erythroid cell maturation and the change of pyruvate kinase (PK) isozymes was studied using fluorescent antibody techniques. The fluorescence of M2‐type PK was strongest in the proerythroblast stage, and then steeply declined with red cell maturation so that only weak fluorescence was seen in orthochromatic erythroblasts. On the other hand, the fluorescence of L‐type PK was seen throughout the maturation of the erythroblasts, with stronger fluorescence in the basophilic or polychromatic erythroblasts than in proerythroblasts.

Glucose 6-Phosphate dehydrogenase variants: A unique variant (G6PD Kobe) showed an extremely increased affinity for galactose 6-phosphate and a new variant (G6PD Sapporo) resembling G6PD Pea Ridge

SummaryTwo new glucose 6-phosphate dehydrogenase (G6PD) variants associated with chronic nonspherocytic hemolytic anemia were discovered. G6PD Kobe was found in a 16-year-old male associated with hemolytic crisis after upper respiratory infection. The enzyme activity of the variant was about 22% of that of the normal enzyme. The main enzymatic characteristics were slower than normal anodal electrophoretic mobility, high Km G6P, increased thermal-instability, an acidic pH optimum, and an extremely increased affinity for the substrate analogue, galactose 6-phosphate (Gal-6P).G6PD Sapporo was found in a 3-year-old male associated with drug-induced hemolysis. The enzyme activity was extremely low, being 3.6% of normal. In addition, this variant showed high Ki NADPH and thermal-instability.G6PD Kobe utilized the artificial substrate Gal-6P effectively as compared with the common natural substrate, glucose 6-phosphate. In G6PD Sapporo, NADPH could not exert the effect of product inhibition. The structural changes of these variants are expected to occur at the portions inducing conformational changes of the substrate binding site of the enzyme.

A unique electrophoretic slow-moving glucose 6-phosphate dehydrogenase variant (G6PD Asahikawa) with a markedly acidic pH optimum

SummaryA new glucose 6-phosphate dehydrogenase (G6PD) variant associated with chronic nonspherocytic hemolytic anemia was discovered in Japan. The patient showed hemolytic crises after upper respiratory infections. The enzyme activity was about 3.8% of the normal. The partially purified enzyme revealed slow anodal electrophoretic mobility, high Km NADP, marked thermal-instability, and increased affinity for a substrate analogue (deamino-NADP). A particular characteristic of this enzyme was a biphasic pH curve with a greatly increased activity at low pH values. From these results, this variant was clearly different from hitherto observed G6PD variants, and was designated G6PD Asahikawa.

G6PD Sendagi: A new glucose-6-phosphate dehydrogenase variant associated with congenital hemolytic anemia

SummaryA new glucose-6-phosphate dehydrogenase (G6PD) variant associated with chronic nonspherocytic hemolytic anemia was discovered. It was found in a 2-year-old male who had a hemolytic crisis after an upper respiratory tract infection. The enzyme activity of the variant was 8.4% of that of the normal enzyme. The enzymatic characteristics were slower than normal anodal electrophoretic mobility, low Km G6P, normal Km NADP, increased utilization of substrate analogues, high Ki NADPH, decreased heat stability, and an alkaline pH optimum. From these results, this was considered to be a new variant and was designated G6PD Sendagi.

Gd(-) Gifu and Gd(-) Fukuoka. Two new variants of glucose-6-phosphate dehydrogenase found in Japan

SummaryTwo new glucose-6-phosphate dehydrogenase (G6PD) variants were discovered in Japan. The first, found in a 9-year-old male, was associated with chronic hemolysis and hemolytic crises after upper respiratory infections. The enzyme activity of the variant was 2.9% of normal. The patients G6PD showed an increased utilization of substrate analogue, deamino-NADP, and thermal instability. The second variant occurred in a 7-year-old male with druginduced hemolysis. The main enzymatic characteristics were reduced enzyme activity, being 6.4% of normal, faster-thannormal anodal electrophoretic mobility, slightly high Michaelis constant for glucose-6-phosphate, thermal instability, and biphasic pH optima. Enzymatic properties of these variants allowed each to be distinguished from previously reported variants. The first variant was designated Gd (-) Gifu and the other, Gd (-) Fukuoka.

Red‐Cell Enzyme Activities and Properties of Mutant Pyruvate Kinase after 1‐Year Storage in a ‐80°C Freezer

Abstract. Red cells from 5 healthy adults and an unstable mutant pyruvate kinase (PK), PK Maebashi, were stored for 12 months in a ‐80°C freezer. With an exception of triosephosphate isomerase and phosphoglycerate kinase activities, normal red‐cell enzyme activities remained essentially unchanged. Mutant PK was characterized by the methods recommended by the International Committee for Standardization in Haematology (ICSH). Normal control and PK Maebashi remained essentially unchanged in their characteristics after storage in a ‐80°C freezer for 12 months. These results indicate that the red cells stored over a long term in a ‐80°C freezer can be used for the study of unstable mutant PK.