Phosphoglycerate kinase, isolated from rabbit muscle in highly purified crystalline form, was compared in terms of chemical, physical and kinetic properties to yeast phosphoglycerate kinase. A summary of the data is presented. Both proteins are composed of a single polypeptide chain, and in electrophoresis only one band was found. The N‐terminus is masked. The C‐terminal amino acid of the muscle enzyme is valine. Muscle and yeast enzyme have nearly identical molecular weights, Michaelis‐Menten constants, optimal pH values and Vmax. On the other hand, they differ significantly in their amino acid composition, especially in the content of sulfur and aromatic amino acids, in electrophoretic mobility and in heat stability. The muscle enzyme has an essential SH group. The single SH group of the yeast enzyme is apparently without importance for enzyme activity. Differences in the same direction as those observed with yeast and muscle phosphoglycerate kinase are discussed in connection with other glycolytic enzymes from the same organisms.

Triose phosphate isomerase was isolated from brewer's yeast and rabbit liver and was obtained in crystalline form. Chemical, physical and kinetic properties were compared to rabbit muscle triose phosphate isomerase. The molecular weight of all three enzymes is in the range of 56000 to 60000. In dodecyl sulfate or as modified maleylated protein, the enzymes dissociate into two polypeptide chains each having a molecular weight in the range of 24000 to 29000. The rabbit muscle and liver enzymes appear to be indistinguishable in terms of their amino acid composition, electrophoretic mobility, kinetic properties, inhibition sensitivity, pH optimum, molecular weight and N‐terminal amino acid (alanine). The yeast enzyme, on the other hand, was found different in the following respects; it has a several fold lower content of sulfur amino acids, is highly resistant to inactivation through photooxidation as well as sulfhydryl and alkylating agents. Furthermore, it contains different N‐terminal amino acids (valine and alanine) and has kinetic properties differing from those of the rabbit enzymes. The crystalline liver and muscle enzymes could be resolved into three distinct electrophoretic forms in starch and polyacrylamide gels. The possible interpretation of the multiple forms in terms of hybrids or conformers is discussed.

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A new triosephosphate isomerase (TPI) variant is described in an 8-year-old Turkish girl suffering from chronic haemolytic anaemia, myopathy and developmental retardation since early infancy. The enzyme activity profile revealed a generalized deficiency in erythrocytes, granulocytes, mononuclear blood cells, skeletal muscle tissue and cerebrospinal fluid. The concentration of enzyme substrate dihydroxyacetone phosphate was distinctly elevated. Biochemical examination showed accelerated enzyme deamidation, the first step in the normal catabolism of TPI during aging of the erythrocyte. The specific activity of the variant TPI, determined by antibody titration, was reduced to 61% of normal. Its heat stability was markedly decreased. Muscle biopsy and neuropsychological testing further clarified the pathogenesis of the disorder. A prevalent alteration of mitochondria similar to that seen in mitochondrial myopathy and an elevated amount of intracellular glycogen were found. The patient's retarded intellectual development was mainly due to impaired visual perception and sensory-motor co-ordination in addition to a lack of syllogistic reasoning. The findings indicate that the low TPI activity leads to a metabolic block of the glycolytic pathway and hence to a generalized impairment of cellular energy supply.

An X-chromosome linked phosphoglycerate kinase deficiency in erythrocytes and leucocytes was discovered in a large German kindred. Seven males of two generations were found to have only 21% of the normal enzyme activity in their erythrocytes, and twelve females of three generations showed various degrees of this defect. The differences in the expression of the deficiency in heterozygote females are explained by the Lyon hypothesis. The deficiency is caused by a variant enzyme, named phosphoglycerate kinase München. Although it differs from the normal enzyme electrophoretically, the two enzymes resemble one another closely in many respects. They have essentially the same Km for the substrates of the backward reaction, identical pH optima and similar rates of thermal inactivation. In contrast to the nine previously described phosphoglycerate kinase deficiencies, all of which are associated with haemolytic anaemia, the carriers of phosphoglycerate kinase München show no overt clinical symptoms. The erythrocyte concentrations of adenine nucleotides and 2,3-diphosphoglycerate are normal.