Isao Yamazaki

The mechanism of indoleacetic acid oxidase reaction catalyzed by turnip peroxidase

Abstract In the iron-reducing activity of peroxidase in the presence of indoleacetic acid as electron donor, the kinetic and stoichiometric evidence supports a free-radical mechanism in which peroxidase catalyzes the formation of 2 moles indoleacetic acid radicals at the expense of 2 moles indoleacetic acid and 1 mole hydrogen peroxide. Inability of peroxidase to catalyze peroxidation of indoleacetic acid under anaerobic conditions is attributed to inactivating action of free radicals upon the enzyme, which is prevented by the addition of some oxidants. The effects of carbon monoxide and Mn 2+ were also examined.

The effect of intracellular oxygen concentration on lactate release, pyridine nucleotide reduction, and respiration rate in the rat cardiac tissue.

By measuring the absorbance change due to myoglobin oxygenation in hemoglobin- free isolated perfused rat hearts, we analyzed effects of perfusion pressure and heart rate upon the intracellular oxygen concentration. With Langendorff perfusion, the cardiac tissue was kept normoxic (above 50 μM O2) at aortic pressure above 50 cm H2O, but became hypoxic (8μM O2) at 30 cm H2O. The increase in cardiac work, expressed as the product of peak systolic pressure and heart rate, increased oxygen consumption at aortic pressure of 50–200 cm H2O. The heart was kept normoxic under these conditions. Lactate release, oxygen consumption, and the oxidation- reduction state of pyridine nucleotide were measured as a function of myoglobin oxygenation under various normoxic and anoxic conditions. Pyridine nucleotide fluorescence and lactate release started to increase as the intracellular oxygen concentration decreased to 6 and 10 μM, respectively. Oxygen consumption was kept constant until the oxygen concentration decreased to 10μM and slowed down below it. A close relationship between oxygen consumption and lactate release was observed. Infusions of epinephnne and norepinephrine under normoxic perfusion conditions increased cardiac work, oxygen consumption, and lactate release. More than 50% of myoglobin was then deoxygenated even under normoxic perfusion conditions. The increase in lactate release was ascribable to the increase in glycolytic flux caused by hypoxia. The change of pyridine nucleotide fluorescence by epinephrine was also explained by hypoxia in cardiac tissue.

The reduction of methylene blue catalyzed by the turnip peroxidase

Abstract In the presence of hydrogen peroxide, crystalline turnip peroxidase catalizes a hydrogen-transferring reaction provided that suitable H-donor and H-acceptor are present. In this reaction triose reductone and dihydroxymaleic acid serve as H-donor, and methylene blue, thionine, and gaseous oxygen as H-acceptor.

PEG-Inhibitor Conjugates: Application of Diphenyl α-Aminoalkylphosphonate to Removal of Chymotrypsin

Diphenyl 1-amino-2-phenylethylphosphonate was introduced to poly(ethylene glycol)s (PEGs) with average molecular masses of 300, 400, and 600 to prepare water-insoluble PEG-inhibitor conjugates. Interestingly, only the conjugate from PEG with an average molecular weight of 600 formed a precipitate with chymotrypsin but not with trypsin. The results demonstrated that the PEG-inhibitor conjugate is useful for separation of chymotrypsin.

Selective Removal of Chymotrypsin Using Diphenyl α-Aminoalkylphosphonate Immobilized on Sepharose Gel

A diphenyl α-aminoalkylphosphonate derivative, which is an irreversible inhibitor of chymotrypsin-like serine proteases, was immobilized on cyanogen bromide-activated Sepharose, and the selective binding of chymotrypsin to the obtained inhibitor-gel was evaluated using batch and column methods. Complete removal of chymotrypsin in an aqueous solution was done using the column method, while partial removal was done using the batch method.

Studies on the Retrogradation of Starch. Part 2. Effect of the Guanidine Hydrochloride on the Retrogradation of Waxy Corn Starch.

粉末X線回折とフーリエ変換赤外分光分析(FT-IR)を用いて研究した.粘度は保存期間とともに増加した.一方,糊化前にGu-HC1を添加しても粘度は保存期間とともに増加し,添加量が多いほど粘度は低かった.膨潤した粒子の相互作用により,それら粒子は水素結合により網目構造を形成する.デソプンの粘度の増加率の長期的な増加は可逆的な結晶化と,貯蔵中の粒子間内の分子間水素結合と関係する.そこでこれらの老化した糊液のX線回折を測定すると,B型の結晶構造の回折線が観測された.また糊化直後と老化後の糊液のFT-IRを測定すると,水素結合を示す3000-3800cm-1の波数でピークの相違を観測し,五つのピークがこの波数内で重なり合っていた.これらの結果から老化の際に,Gu-HC1がワキシコーンスターチの分子構造に与える変化を提案し,模式図として示した.

A Study on the Retrogradation of Waxy Corn Starch.

ワキシコーンスターチ糊液の老化を示差走査熱量測定(DSC)と粉末 X 線回折を用いて研究した。DSC は -15℃ から 15℃ ,および 30 から 100℃ の温度範囲で測定した。糊化直後の糊液では 0℃ 付近に鋭い吸熱ピークが観測され,これ以外に吸熱は観測されなかった。長期放置して糊液が老化すると 50℃ 付近に再糊化の吸熱ピークが観測され,また 0℃ 付近の吸熱ピークは二つに分かれた。これら両者の吸熱ピークは互いに関連しており,ともに老化の結果であると考えられる。一方,糊液を凍結させて放置したところ, 72 日経過しても老化に起因する吸熱ピークは観測されなかった。また,老化した糊液中のワキシコーンスターチの X 線回折を測定すると B 型の結晶構造の回折線が観測された。また 3 種類の濃度の糊液を調製し,老化挙動を比較したところ,老化の速度は著しく影響を受けたのに対し,デンプン乾物量換算した吸熱量はほぼ一定の値になった。このことは糊液老化の機構が濃度により影響を受けないことを示している。これらの結果から糊化,老化の際のワキシコーンスターチの分子構造の変化を提案し,模式図として示した。