Alteration of thermal stability of glucose oxidase associated with the redox states

By the method of differential scanning calorimetry, it was found that thermal stability of glucose oxidase was dependent on its redox states. The oxidized form showed an apparent denaturation temperature at 76°C and the denaturation enthalpy was approximately 865 kcal/mol. On reduction of the enzyme, the denaturation temperature increased by about 10°, but no significant change was seen in the denaturation enthalpy. The activation energies of the denaturation of the oxidized and the reduced enzymes were about 89 and 103 kcal/mol, respectively. These results may imply conformational changes in the catalytic turnover of this enzyme.     

Continuous synthesis of the dnaA gene product of Escherichia coli in the cell cycle

Summary The dnaA gene product of Escherichia coli, identified as a weakly basic protein of about 48,000 daltons (Yuasa and Sakakibara 1980), can be separated from other celluar proteins by means of two-dimensional gel electrophoresis. Synthesis of the dnaA protein took place continuously during a cell growth cycle. The newly synthesized dnaA protein persisted stably for one generation. Thermosensitive dnaA protein produced by the dnaA167 mutant was stable at 30° C, but was disintegrated at 42° C. The amount of intact dnaA protein present in the mutant exposed to the high temperature for 60 min was less than a quarter of the amount at the time of the shift. The cells having the reduced amount of intact dnaA protein were capable of initiating a new round of chromosome replication at the low temperature without de novo synthesis of the dnaA protein. The potential of the mutant for initiation of DNA replication decreased with reduction in the amount of the thermoreversible dnaA protein. The mutations dnaA167 and dnaA46 had no significant effect on the syntheses of the dnaA mRNA and the protein product at the low and high temperatures.Abbreviations used SDS sodium dodecyl sulfate - kb kilobase pairs - TCA trichloroacetic acid     

Participation and Properties of Lipoxygenase and Hydroperoxide Lyase in Volatile C6-Aldehyde Formation from C18-Unsaturated. Fatty Acids in Isolated Tea Chloroplasts

Isolated tea chloroplasts utilized linoleic acid, linolenicacid and their 13-hydroperoxides as substrates for volatileC₆-aldehyde formation. Optimal pH values for oxygen uptake,hydroperoxide lyase and the overall reaction from C₁₈-fattyacids to C₆-aldehydes were 6.3, 7.0 and 6.3, respectively. Methyllinoleate, linoleyl alcohol and -linolenic acid were poor substratesfor the overall reaction, but linoleic and linolenic acids weregood substrates. The 13-hydroperoxides of the above fatty acidsand alcohol also showed substrate specificity similar to thatof fatty acids. Oxygen uptakes (relative V_max) with methyl linoleate,linoleyl alcohol, linolenic acid, -linolenic acid and arachidonicacid were comparable to or higher than that with linoleic acid.In winter leaves, the activity for C₆-aldehyde formation fromC₁₈-fatty acids was raduced to almost zero. This was due tothe reduction in oxygenation. The findings presented here provideevidence for the involvement of lipoxygenase and hydroperoxidelyase in C₆-aldehyde formation in isolated chloroplasts. (Received July 11, 1981; Accepted November 5, 1981)     

Fungal contamination and mycotoxin-producing potential of dried beans

A total of 604 samples of about 7 different types of beans was examined to determine their mycological profiles, and suitability for use as solid substrates for mycotoxin production.All of the samples were collected from bean jam makers in Tokyo by the official food examiners.Genera Penicillium and Aspergillus were predominant, and genus Wallemia was also found commonly in all types of beans.Mycotoxin-producing Aspergillus strains were isolated from 52 samples of beans, approximately 9% of the total. The highest incidence of toxigenic Aspergillus (14.1%) was found in kidney beans. Red beans and peas inoculated with Aspergillus ochraceus were found to produce about 7 to 8 times more toxin than was obtained in a liquid medium, and red beans inoculated with A. versicolor produced more toxin than was obtained in yeast extract sucrose broth. Green peas inoculated with Fusarium graminearum produced about 8 times more T-2 toxin than was obtained in 1% peptone containing Czapek solution under comparable culture conditions.     

Enzymatic preparation of organometallic compounds with second-order optical nonlinearities

Twelve species of optically active metallocene derivatives having a 4-nitrophenyl group were prepared with horse liver alcohol dehydrogenase- or lipase-catalyzed optical resolution as the key step. The second harmonic generation (SHG) efficiently of these products was measured by the power method using the fundamental light from the Nd:YAG laser. (-)-1- (4-Nitrophenylthio)ethylferrocene (9), (+)-1-(4-nitrophenylthio)ethylruthenocene (16), (+)-1-(4-nitrophenylthio)ethylosmocene (19), (+) -1-(5-nitro-2-pyridylthio)ethylruthenocene (21), and (+) -1-[(4-nitrophenylhydrazono)methyl] -2-methylferrocene (12) showed SHG signals. The highest SHG efficiency was found with (+) -16, being 27 times more intense than the commonly used urea standard.     

A Novel Glial Growth Inhibitory Factor, Gliostatin, Derived from Neurofibroma

Neurofibroma tissue was investigated for the presence of glial growth modulators that would suppress the proliferation of glial cells. A novel endogenous polypeptide inhibitor of proliferation and DNA synthesis in glial cells, gliostatin, was purified from the extracts of neurofibroma by a procedure comprising dye and anion-exchange column chromatography, and HPLC. A monoclonal antibody raised against partially purified gliostatin showed no cross-reactivity with known cytokines, but adsorbed the growth inhibitory activity of gliostatin and immunochemically visualized the putative gliostatin bands on western blot analyses. Although the product showed an apparent M(r) of 100,000 accompanied by an inhibitory activity on gel filtration column chromatography, it migrated at a lower apparent M(r) of 50,000 under the reducing conditions on western blotting, indicating that a homodimeric structure of native gliostatin consisted of 50-kDa subcomponents. Gliostatin was a potent growth inhibitor acting at nanomolar concentrations against all glial tumor cells and glia maturation factor-stimulated astroblasts, but not neuronal cells.     

Protoclonal variation of plant regeneration in rice

Protoplasts were isolated from callus derived from a single homozygous seed of Oryza sativa L. var. Norin 8. Thirty protoclones were randomly selected and these showed variation in regeneration frequency ranging from 0–87% with an average of 52%. The potential for regeneration of each protoclone as reflected in the regeneration frequency was analyzed five times over a period of 250 days and showed that the protoclones can be classified into three types, namely: protoclones with high regeneration frequency; protoclones with low regeneration frequency, both of which maintained their respective levels of regeneration potential; and protoclones with gradually decreasing regeneration frequency. Secondary protoclones established from protoplasts isolated from some of these protoclones and regenerated 2–3 times for a period of 120 days also showed further reduction in regeneration frequency. The polypeptide composition analyzed by two dimensional gel electrophoresis suggests the presence of specific polypeptides related to regeneration potential. Analysis of ploidy level based on plant morphology and pollen size suggests the predominance of tetraploids among the regenerated plants.     

Temperature dependence of optical properties of chlorophyll a incorporated into phosphatidylcholine liposomes

Temperature-dependent spectral changes of chlorophyll a (Chl a) incorporated into liposomes of two types of phosphatidylcholine are studied. When Chl a incorporated into the liposomes is cooled down to 5°C from the temperature of the gel-to-liquid crystalline phase transition of the lipid, the red shift as well as the increase in half-bandwidth of the red peak of Chl a are only slight. By measuring the difference spectra produced by substracting the absorption spectrum at the phase transition temperature of the lipid from that at lower temperature, it is shown that the component absorbing at longer wavelength (675–685 nm) than the peak of the red maximum (about 670 nm) significantly increases at the expense of the component absorbing at shorter wavelength (657–668 nm). The positions of positive and negative peaks depend on the temperature and the molar ratio of the lipid to Chl a. The absorbance change is most pronounced on cooling below the phase transition temperature of the lipid. The temperature-induced absorbance change is almost completely reversible. The results indicate that the aggregated forms of Chl a in liposomes can be spectrophotometrically detected in the gel phase of the lipid.     

Structural abnormalities of the Y chromosome and abnormal external genitals

Summary Three infants with different types of Y-chromosome abnomalies, including short- and/or long-arm deletion and mosaicism, are reported. The karyotypes of these patients were: 45,X/46,X,del(Y)/47,X,del(Y), del(Y) on peripheral lymphocytes and 45,X/46,X, del(Y) on gonadal tissue (case 1), 45,X/46,X,del(Y) (case 2), and 45,X/46,X,r(Y) (case 3). In case 1 the euchromatic segment on the deleted Y was distinctly larger than that of the father's Y.The three infants had no gross phenotypic anomalies except ambiguous genitals and low birth weight, and they were small for date. The histologic diagnosis in two of them was mixed gonodal dysgenesis (cases 1 and 2).The relationship between structural abnormalities of the Y chromosome and ambiguous genitals as well as male-determining factors is discussed.     

Diffusion of H-meromyosin in F-actin plus ATP solution at a very low electrolyte concentration

The translational diffusion coefficient (D) of H-meromyosin in actin (F-actin) and ATP solution was measured under conditions wherein the actin-activated ATPase activity is close to its maximal value at a very low electrolyte concentration. The results were compared with similar data obtained with 0.1 M KCl, where H-meromyosin and actin were almost completely dissociated. With 0.1 M KCl, it was found that there was no dependence of the D of H-meromyosin on actin concentration. On the other hand, at a very low electrolyte concentration, it was found that the D of H-meromyosin did depend on actin concentration; at a rather high actin concentration (and activation of ATPase), it was slightly larger than at low or zero actin concentrations. This behavior of D at a low electrolyte concentration is interpreted on the assumption that even in solution, H-meromyosin molecules can actively slide on actin filaments due to the ATPase activity.