Breaking action of reductones related to ascorbic acid on nucleic acids

The action of two types of ascorbate-related reductones on nucleic acids was investigated by comparison with that of ascorbic acid (AsA). Amino reductone (ScA) and thiol reductone (MHC) caused strandscissions in nucleic acids. This was confirmed by the fact that reductones lowered the viscosity of DNA solution and shifted the peaks of DNA and RNA to the low molecular side in centrifugal profile. Cu2+ strengthened their action as in the case of enediol reductones. The braking activity of thiol reductone is relatively wesk compared with those of amino and enediol reductones. The preferential degradation of spurinic acid was caused with amino and thiol reductones, suggesting that pyrimidine clusters in nucleic acids were susceptible to breakage.

Characterization of pyruvate kinase from the liver of a patient with aberrant erythrocyte pyruvate kinase, PK Nagasaki

The characterization of the L-type PK were made of PK extracted from the liver of a patient with congenital hemolytic anemia associated with an erythrocyte PK variant, PK Nagasaki. The L-type PK of PK Nagasaki showed the following parameters: slow migration on electrophoresis, high Km for PEP without F-1,6-P2, less activation by F-1,6-P2, normal Km for ADP, high utilization of UDP, acidic pH optimum, and instability to urea and heat. These tests served to differentiate this L-type PK variant from the other variants previously reported. At the same time, both the Km for PEP with F-1,6-P2 saturation and the electrophoretic mobility of L-type PK were found to be different from those of the erythrocyte PK and PK Nagasaki. Though the liver cell, with regard to L-type PK, has only the less functional and less stable mutant L-type PK there is no evidence of liver dysfunction or damage, although there is chronic hemolytic anemia.

Induction and repair of strand breaks and 3'-hydroxy terminals in the DNA of mammalian cells in culture following gamma-ray irradiation

DNA was isolated in a fairly pure and intact state from cultured mouse leukaemia cells (L5178Y) after gamma-ray irradiation using a hydroxyapatite column chromatography method, and analysed further by sucrose gradient centrifugation or DNA polymerase (EC 2.7.7.7, enzyme A of Klenow from Escherichia coli) assay. Irradiation of the cells induced single- and double-strand breaks in the DNA with an efficiency of 100 eV/break and 1300 eV/break, respecitvely. Approximately 50% of the single-strand breaks were estimated to be those arising from allali-labile lesions. A linear, dose-dependent increase was found in the template activity of the DNA, indicating the induction of 3'-OH terminals by gamma-irradiation. Post-irradiation incubation of the cells in serum-free medium allowed the majority of the breaks to rejoin within a few hours. Repair of the alkali-labile lesions was, however, found to be much slower than that of "actual" single-strand breaks. A slight increase of the DNA template activity was found during the period of post-irradiation incubation. The reason for the increase is discussed.

Excision repair of benzo[a]pyrene-deoxyguanosine adducts in baby hamster kidney 21/C13 cells and in secondary mouse embryo fibroblasts C57BL/6J

The formation and excision of benzo[a]pyrene-deoxyguanosine adducts in metabolizing baby hamster kidney cells (21/C13) and secondary mouse embryo fibroblasts (C57BL/6J) was investigated. Both diastereomeric adducts, N2-(10-(7beta,8alpha,9alpha-trihydroxy-7, 8, 9, 10 tetrahydrobenzo[a]-7,8,9,10-tetrahydrobenzo[a]pyrene)yl)deoxyguanosine, were detected in both cell lines and both cell lines were capable of excising these lesions, albeit with low efficiency.

A new pyruvate kinase variant (PK Osaka) demonstrated by partial purification and condensation

A qualitative variant of erythrocyte and liver pyruvate kinases (PK Osaka) was detected in a family in which two siblings have extremely low PK activity by semipurification with DEAE cellulose chromatography and subsequent concentration of the enzyme solutions. This was previously reported to be a quantitative variant based on studies of crude tissue preparations. The molecular aberrations were characterized by slow mobility upon electrophoresis, abnormal kinetics for phosphoenolpyruvate, and low affinity for anti-human erythrocyte PK serum. The mutant PK L was similar both electrophoretically and immunologically to PK R.

Isoelectric focussing of normal human erythrocyte pyruvate kinase (PK) and PK variants with abnormal electrophoretic patterns

Isoelectric points of normal human erythrocyte pyruvate kinase (PK) and PK variants with abnormal electrophoretic patterns, were obtained by means of isoelectric focussing. The obtained isoelectric points of normal, PK Nagasaki, PK Tokyo II, PK Ube, and case T.S. were 7.36, 7.38, 7.05, 6.90, and 7.04, respectively, at 6 degrees C. All of the PKs collected after isoelectric focussing were shown to be not of the L-type PK but to be the erythrocyte PK (by means of thin-layer-polyacrylamide gel electrophoresis). The PKs with fast migration had isoelectric points that were shifted to the acidic side as compared with those of the normal subjects. The PK with slow migration had an isoelectric point that was shifted to the alkaline side, demonstrating that the isoelectric points obtained by isoelectric focussing were consistent with the electrophoretic patterns of the crude hemolysates. Isoelectric focussing also revealed the existence of PK variants with abnormal electric net charge, just as well as thin-layer-polyacrylamide gel electrophoresis.

Evidence for caffeine-sensitive damage in methylazoxymethanol acetate-treated L5178Y cells

The effects of methylazoxymethanol (MAM) acetate on colony survival, cell proliferation and DNA synthesis of murine lymphoma L5178Y cells are studied. Decreased sensitivity and immediate depression of cell proliferation and DNA synthesis were found in L5178Y cells in contrast to the reports on HeLa cells. Pre-labelling with 5-bromodeoxyuridine (BUdR) did not enhance significantly the carcinogen-induced cell lethality. Post-treatment with caffeine greatly enhanced cell lethality and depression of cell proliferation. These effects of caffeine were diminished when the cells had passed through two generations following the MAM acetate treatment. Experiments with synchronized cells showed that the action of caffeine was located primarily in S phase following the MAM acetate-treatment. These results strongly suggest that in L5178Y cells, MAM acetate induces damage, which is repaired by a mechanism analogous to post-replication repair of UV light-induced damage.

Electrophoretic, immunologic and kinetic characterization of erythrocyte pyruvate kinase in the Basenji dog with pyruvate kinase deficiency

The electrophoretic mobility and the immunologic specificity of erythrocyte pyruvate kinase (PK) of the homozygous Basenji dog with PK deficiency were identical to those of normal M2-type PK isozyme seen in the white cell but not to those of the erythrocyte PK isozyme. Kinetic properties and stability were also consistent with the M2-type PK isozyme. Defective PK in the homozygous red cell was due to the absence of the erythrocyte PK isozyme and the compensatory presence of M2-type PK isozyme, as seen in the severe classical type PK deficiency in man.

Breaking action of ascorbic acid on nucleic acids

The lowering of the viscosity of DNA solution was caused by the action of AsA or EA and facilitated in the presence of CU2+. However, the action of AsA-3-P was very weak. By sucrose density gradient centrifugation, it was observed that single- and double-strand scissions of DNA were provoked by AsA or EA and enhanced with Cu2+, while only a single-strand scission was caused by AsA-3-P and Cu2+. Similar action of AsA or AsA-3-P was also observed for RNA. Thus, the result indicates that the enediol group of AsA takes an essential part in the breakage of nucleic acids, and Cu2+ enhances the action. It was shown that Apu was mainly decomposed by AsA, whereas Apy not, suggesting that some pyrimidine cluster may be one of the regions attacked by AsA. During the reaction with DNA, the reducing activity of AsA decreased first to some extent and then increased, whereas the reducing activity of AsA-3-P was much lower than that of AsA and decreased steadily. The priming activity of DNA for DNA polymerase was changed after treatment with AsA according to the condition. It was enhanced when DNA was treated under mild conditions but decreased with severer action.

Four new pyruvate kinase (PK) variants and a classical PK deficiency

Four new red-cell pyruvate kinase (PK) variants are presented along with one case of so-called classical type PK deficiency. PK 'Tokyo II' had a low activity, Km (PEP) and Vmax, but a normal urea stability and only slight deviation from normal in neutralization tests by antiserum. It had a normal nucleotide specificity, abnormal electrophoretic mobility (fast moving) and the variant was associated with a mild hemolytic anaemia. PK 'Maebashi' had a low activity, high Km (PEP), low Vmax, urea instability, decreased reactivity to antiserum, normal electrophoretic mobility, normal nucleotide specificity and was associated with a moderate haemolytic anaemia. PK 'Tsukiji' had low activity, high Km (PEP), markedly high Vmax, urea instability, decreased reactivity to antiserum, abnormal electrophoretic mobility (fast moving) and grossly abnormal nucleotide specificity especially abnormal behaviour to ADP. The haemolytic process in this case was moderate to severe. PK 'Ube' was electrophoretically abnormal (fast moving) but otherwise had normal characteristics and the propositus was healthy and not anaemic. PK 'Ube' was found by electrophoretic screening for genetic PK polymorphism. In the classical type PK deficiency, the usual red-cell PK (PK-R1 and PK-R2) was not demonstrable by electrophoresis but instead M2-type PK was present, presumably by compensatory process. Kinetic studies confirmed that the patient's red-cell PK consisted of M2-type PK. This patient had a severe haemolytic anaemia.