Papers - Mashino, Tadahiko

NADPH mediates the inactivation of bovine liver catalase by monochloroamine

Maskino Tadahiko, Fridovich Irwin

Archives of Biochemistry and Biophysics 265 ( 2 ) 279 - 285 1988

Research paper (scientific journal), Joint Work,  ISSN  0003-9861

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<p>Bovine liver catalase suffered a biphasic inactivation when exposed to NH₂Cl. A rapid and irreversible phase of activity loss was followed by a much slower and reversible inactivation. Removal of tightly bound NADPH from the enzyme decreased the extent of the rapid phase; whereas addition of NADPH augmented it. The catalase from Aspergillus niger, which does not contain bound NADPH, was not nearly as sensitive toward NH₂Cl as was the liver enzyme and was not sensitized by added NADPH. NADPH is oxidized by NH₂Cl, as evidenced by loss of the 340-nm absorption band, but the product of this oxidation was not NADP⁺. The rapid inactivation of liver catalase by NH₂Cl was accompanied by some bleaching of the bands in the visible, while the slow inactivation was coincident with the appearance of a new band at 570 nm. A tentative explanation for these observations is proposed. © 1988.</p>

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Effects of urea and trimethylamine-N-oxide on enzyme activity and stability

Mashino Tadahiko, Fridovich Irwin

Archives of Biochemistry and Biophysics 258 ( 2 ) 356 - 360 1987.11

Research paper (scientific journal), Joint Work,  ISSN  0003-9861

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<p>The interactions of urea, trimethylamine-N-oxide (TMAO), and related solutes on a number of enzymes were examined. Urea inhibited enzymatic activity and accelerated the thermal inactivation of catalase, whereas TMAO activated some enzymes but inhibited others. The effects of urea and of TMAO, whether parallel or in opposition, were exerted independently. Thus, in those cases where TMAO increases enzymatic activity, it did so to the same relative degree, whether or not urea was present. TMAO markedly decreased the rate of thermal inactivation of catalase, indicating that it does favor compact protein structures. The assumption that TMAO factors compaction of protein structure, whereas urea has the contrary effect, does not lead to the expectation that TMAO must always oppose the effect of urea on enzymatic activity, since the most compact form of an enzyme may not always be the most active form. © 1987.</p>

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Superoxide radical initiates the autoxidation of dihydroxyacetone

Mashino Tadahiko, Fridovich Irwin

Archives of Biochemistry and Biophysics 254 ( 2 ) 547 - 551 1987.05

Research paper (scientific journal), Joint Work,  ISSN  0003-9861

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<p>The aerobic xanthine oxidase reaction causes the cooxidation of dihydroxyacetone in a process which is strongly inhibited by superoxide dismutase but not by catalase, HO · scavengers, or iron-inactivating chelating agents. Several molecules of the sugar can be oxidized per O₂^- introduced. A free radical chain mechanism, in which O₂^- acts both as an initiator and as a chain propagator, is proposed. Simple sugars capable of tautomerizing to enediols may now be added to the list of biologically relevant targets for O₂^-. © 1987.</p>

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Base liberation from nucleotides by superoxide and intramolecular enhancement effect of phosphate group

Yamane Hiroshi, Yada Nobuhisa, Katori Etsu, Mashino Tadahiko, Nagano Tetsuo, Hirobe Masaaki

Biochemical and Biophysical Research Communications 142 ( 3 ) 1104 - 1110 1987.02

Research paper (scientific journal), Joint Work,  ISSN  0006-291X

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<p>The reaction of nucleotides with superoxide gave the corresponding nucleobases in good yield. The base-release reaction of nucleotides due to superoxide was examined and compared to that of nucleosides. Hence, the phosphate moiety greatly enhances the yields, in particular those of adenine from adenosine monophosphates. Superoxide in combination with the phosphate moiety has been revealed to be more active than superoxide alone. The phosphate peroxy radical, generated in situ from superoxide and phosphate, seems to be the species responsible for the formation of the free bases. © 1987.</p>

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Mechanism of the cyanide-catalyzed oxidation of α-ketoaldehydes and α-ketoalcohols

Mashino Tadahiko, Fridovich Irwin

Archives of Biochemistry and Biophysics 252 ( 1 ) 163 - 170 1987

Research paper (scientific journal), Joint Work,  ISSN  0003-9861

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<p>Cyanide catalyzes the reduction of dioxygen or of ferricytochrome c by dihydroxyacetone phosphate. The rapid initial phase of these reactions, but not the subsequent slow phase, was augmented by incubating the triose phosphate aerobically or anaerobically at pH 9.0 prior to adding the cyanide. The aerobic incubation, which was most effective, was associated with a decline in enediol, whereas the less effective anaerobic incubation was accompanied by an increase in enediol content. This suggested that the α-ketoaldehyde product of autoxidation of the enediol, rather than the enediol itself, was responsible for the rapid phase reaction which followed addition of cyanide. This was confirmed by exploring the cyanide-catalyzed oxidation of the α-ketoaldehyde, phenylglyoxal. The inhibitory effect of the manganese-containing superoxide dismutase indicated that O₂^- was a kinetically important intermediate of the rapid phase reaction. A reaction mechanism is proposed which is consistent with the results presented. © 1987.</p>

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α,β-Dihydroxyisovalerate dehydratase. A superoxide-sensitive enzyme

Kuo C. F., Mashino T., Fridovich I.

Journal of Biological Chemistry 262 ( 10 ) 4724 - 4727 1987

Research paper (scientific journal), Joint Work,  ISSN  0021-9258

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<p>Increasing the intracellular flux of O₂^- by incubating aerobic Escherichia coli with paraquat or plumbagin markedly lowered the α,β-dihydroxyisovalerate dehydratase activity detectable in extracts from these cells. This effect was not seen in the absence of dioxygen and was exacerbated by inhibiting protein biosynthesis with chloramphenicol. These effects of paraquat and of plumbagin were both time- and concentration-dependent. Transfer of E. coli from aerobic to anaerobic conditions caused a rebound of the dehydratase activity, in the continued presence of paraquat and of chloramphenicol, indicating the presence of a mechanism for reactivating this enzyme. The instability of the dehydratase activity in cell extracts was exacerbated by selective removal of superoxide dismutase, but not of catalase, by immunoprecipitation. Addition of exogenous superoxide dismutase reversed the effect of immunoprecipitation; whereas catalase or inactive superoxide dismutase were ineffective. We conclude that the dehydratase is inactivated by O₂^-. This could account for the bacteriostatic effects of dioxygen and of paraquat.</p>

Epoxidations of olefins by peroxy intermediate generated in situ from CCl₄ and superoxide

Yamamoto Hiroshi, Mashino Tadahiko, Nagano Tetsuo, Hirobe Masaaki

Journal of the American Chemical Society 108 ( 3 ) 539 - 541 1986

Research paper (scientific journal), Joint Work,  ISSN  0002-7863

Reduction of imines by cluster [Fe₄S₄(SR)₄]^3-

Mashino Tadahiko, Nagano Tetsuo, Hirobe Masaaki

Tetrahedron Letters 24 ( 46 ) 5113 - 5116 1983

Research paper (scientific journal), Joint Work,  ISSN  0040-4039

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<p>The clusters [Fe₄S₄(SR)₄]^n- (n=3) generated electrochemically reduced imines to amines in a CH₃CN/CH₃OH solution. The correlations between the redox potentials of imines and the yields of the reductions were examined. © 1983.</p>

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