Partial characterization of protein tyrosine kinase activity in normal and leukemic human myeloid cells.

We have examined the expression of the protein tyrosine kinase (PTK) encoding oncogenes fes and abl in normal and malignant human myeloid cells in immunoblotting experiments. fes was markedly present in all cytosolic and most membrane fractions of normal and malignant cells. abl was only visible in normal cells, and occurred mostly in the cytosolic fractions. Molecular weights of identified proteins were different from the known products of fes and abl, possibly by alternative splicing at the mRNA level or by proteolysis. PTKs in myeloid cells were further purified by fast liquid protein chromatography (FPLC). PTK-activities of column fractions were assayed using a solid-phase non-radioactive dot-blot assay. Cytosolic and membrane fractions showed a FPLC pattern with a constant as well as a variable part in both normal and malignant cells, possibly indicative for PTKs with specialized functions in normal cell growth and transformation. Partial characterization of PTKs from different eluted peaks of AML-M4 blast cells demonstrated that PTKs from these peaks are kinetically distinct from each other.

Tyrosine protein kinase activity in normal and leukaemic human blood cells.

Tyrosine protein kinase (TPK) activity was measured in subcellular fractions of normal granulocytes, lymphocytes and monocytes, and acute and chronic myeloid and lymphoid leukaemic cells. Of several tested tyrosine-containing substrates, poly (glutamic acid: tyrosine = 4:1) (S1) proved to be the best synthetic substrate. High cytosolic TPK activity was found in every cell type. Different TPKs may exist in various cell fractions, as was indicated by the difference in Km values for S1 in cell fractions of normal granulocytes and lymphocytes. No significant difference was found in total TPK activity between normal and leukaemic cells, indicating that total TPK activity is not related to the leukaemic process itself. A highly significant difference was found in membrane fractions in normal granulocytes and M1-M2 AML cells versus normal monocytes and M4-M5 AML cells, suggesting an association between TPK activity and monocytic differentiation in these cell fractions.

Isozyme pattern of enolase of childhood tumors.

Retinoblastoma, neuroblastoma, and medulloblastoma have many common features, clinical as well as histologic; a common embryonic origin has been suggested. The authors studied the electrophoretic pattern of enolase (EC 4.2.1.11) in these tumors. All tumors were characterized by the presence of three types of enolase, designated as alpha alpha, alpha gamma and gamma gamma. The latter is supposed to be the neuron-specific enolase. Normal adult brain and adult retina show the same set of isozymes (alpha alpha, alpha gamma and gamma gamma). In contrast, gliomas of childhood, tumors originating from the supportive tissue of the central nervous system, are characterized mainly by the presence of the alpha alpha dimer and a small amount of the alpha gamma hybrid. The results of this report support the hypothesis of a common embryonic origin of retinoblastoma, neuroblastoma, and medulloblastoma.

Glycolytic enzymes from human neuroectodermal tumors of childhood.

In this study pyruvate kinase, hexokinase and aldolase are investigated in two types of embryonal tumors, neuroblastomas and medulloblastomas; the results are compared with similar studies in gliomas. The activities of hexokinase and pyruvate kinase are significantly decreased in neuroblastomas. In neuroblastoma and medulloblastoma all five forms of pyruvate kinase (K4, K3M, K2M2, KM3 and M4) are present. In contrast, the gliomas investigated are characterized by the presence of mainly K4 and a little K3M. In neuroblastomas, medulloblastomas and gliomas, hexokinase type I is present; in addition, hexokinase type II is present in two medulloblastomas. Aldolase A is the predominant isozyme in all tumors investigated; this is in contrast with normal nervous tissue. It can be concluded that the isozyme characteristics especially of pyruvate kinase from neuroblastomas and medulloblastomas are comparable with similar findings in retinoblastoma; these findings support the hypothesis that these three tumors have a common embryonic origin.

Correlation between cataract and glutathione metabolism.

Riboflavin status was studied in 156 older healthy people living at home in The Netherlands by assaying erythrocyte glutathione reductase (with and without FAD). The average activation coefficient of glutathione reductase was found to be 1.42 +/- 0.19. 7% of the population studied showed cataract (based on the eye examination). It seems that no correlation exists between cataract and riboflavin deficiency.

Characterization of some glycolytic enzymes from human retina and retinoblastoma.

GLycolytic enzymes were studied from normal human retinas (both fetal and adult) and from retinoblastomas of eight patients and an established retinoblastoma cell line. No significant differences were found between the enzyme activities in the tissues investigated except for hexokinase and pyruvate kinase, which were significantly decreased in the tumor cells. In fetal retina, five different forms of pyruvate kinase could be detected by electrophoresis (K4, K3M, K2M2, KM3, and M4). In adult retina the K4 isozyme is almost absent, while in retinoblastoma the M4 isozyme is hardly present. In the retinoblastoma cell line, the M4 isozyme is completely absent. Alanine inhibition of pyruvate kinase from the retinoblastoma cell line is more inhibited compared to the pyruvate kinase of fetal retina and retinoblastoma and is even more inhibited compared to adult retina. Electrophoresis of aldolase from adult retina revealed the presence of all potential A-C hybrids (A4, A3C, A2C2, AC3, and C4). Fetal retina, however, is characterized by the predominance of the A type. The same patterns were observed in the retinoblastoma cell line and retinoblastoma. However, in other brain tumors, e.g., gliomas of adults, a five-membered A-C hybrid set is found. Electrophoresis of hexokinase from normal fetal and adult retina revealed the predominance of hexokinase type I; retinoblastoma and retinoblastoma cell line are both characterized by the presence of considerable amounts of hexokinase type II. The isozyme shifts in retinoblastoma result in an enzyme pattern identical to that of fetal retina except for the presence of hexokinase type II.

Extreme deficiency of L-type pyruvate kinase with moderate clinical expression.

In the erythrocytes and liver of a patient with hereditary non-spherocytic hemolytic anemia and increased serum aminotransferases, almost complete deficiency of L-type pyruvate kinase was detected. The parents of the patient are second cousins and the pyruvate kinase activity in their erythrocytes was decreased to about half normal values. Pyruvate kinase from the patient is characterized by extreme lability. Pyruvate kinase from the parents' red cells showed no molecular abnormalities. No cross-reactive material could be precipitated with a monospecific antibody raised against L-type pyruvate kinase in the patient's erythrocytes. In the red cells of the parents a decreased amount of cross-reactive material against pyruvate kinase antibodies was found, indicating that the lowered pyruvate kinase activity in the erythrocytes of the parents is caused by a decreased level of the pyruvate kinase protein. In the liver of the patient no L-type pyruvate kinase activity and no immunologically recognizable L-type pyruvate kinase could be detected. The increased lability of the enzyme protein may explain the low residual activity. However, this decreased activity is shown to be sufficient to perform a normal glycolytic flux resulting only in moderate clinical expression.

Separation and characterization of hexokinase I subtypes from human erythrocytes.

Hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) type 1 from human erythrocytes exists in four electrophoretical distinct forms, termed Ia, Ib, Ic and Id in order of their increasing anodal electrophoretic mobility at pH 8.8. We were able to separate type Ia, Ib and Icd on phosphocellulose by using a discontinuous gradient elution. The three chromatographically distinct forms do not differ in their affinity constants for the substrates glucose and MgATP2-. In addition the inhibition by glucose 1,6-diphosphate does not differ significantly for all forms. However, the regulation of these inhibitions by inorganic phosphate is much less for type Ia compared to the other subtypes (P = 0.001). Aging of the red cells is accompanied by a relative increase of the proportion of type Ic and Ia, which is the less regulated form of the enzyme. This shift in electrophoretic and regulatory properties is argued to be due to a post-translational modification of the primary enzyme.

Correlation between alanine inhibition of pyruvate and composition of K-M hybrids.

A method is described for determination of the percentage of K-subunits in the K-M set of pyruvate kinase. The method is based on the alanine inhibition of the K-subunits. A linear correlation (r = 0.99) is found between the alanine inhibition and the percentage of K-subunits as calculated from the electropherograms, assuming (a) a subunit distribution as indicated by the suffix in K4, K3M, K2M2, etc., and (b) an equal contribution of K- and M-subunits to the intensity of the stain.

Isozymes of pyruvate kinase from human brain, meningiomas, and malignant gliomas.

Pyruvate kinase isozymes were studied in normal brain tissue (both fetal and adult) and in meningiomas and malignant gliomas. In fetal brain five different forms could be detected by electrophoresis (K4, K3M, K2M2, KM3, and M4). In adult brain the M4-type, K3M hybrid, and K4-type are present; the M isozyme is largely predominant. Alanine inhibition of pyruvate kinase is in agreement with the electrophoretic pattern. Pyruvate kinase from fetal brain and brain of a newborn is more inhibited compared with pyruvate kinase from adult brain. The Lineweaver-Burk plots for pyruvate kinase from fetal brain and brain of the newborn are nonlinear due to the presence of hybrids. Pyruvate kinase from meningiomas and malignant gliomas is strongly inhibited by alanine. Electrophoresis proved the presence of mainly K4 type and the hybrid K3M, which is in agreement with the alanine inhibition. Determination of the Km's for phosphoenolpyruvate supports this conclusion. The determination of the alanine inhibition of pyruvate kinase may be a diagnostic tool in surgery for gliomas.

Alanine inhibition of pyruvate kinase in gliomas and meningiomas. A diagnostic tool in surgery for gliomas?

In gliomas a shift was found in the composition of enzymes, manifested by abnormal inhibition of pyruvate kinase by alanine. This study demonstrates the appearance of the MII-type isoenzyme in various gliomas. This MII type is also found in meningiomas but not in normal brain tissue. The method of enzyme examination described may be valuable as a diagnostic aid in the surgery of gliomas.

Defective erythrocyte pyruvate kinase.

A defective pyruvate kinase (EC 2.7.1.40) is described. The abnormal PK is characterized by a shift in the R in equilibrium T equilibrium to the T-state. The Ko.5 for the substrate phosphoenol pyruvate is about 6 times higher than for the normal enzyme, while the KM value for the positive effector Fru-1, 6-P2 is increased. In agreement with a shift to the T-state is the increased affinity of the abnormal enzyme for the negative effectors ATP and alanine. The results are discussed in relation to other abnormal pyruvate kinases.