Koichiro Honda

Studies on the Metabolism of Monofluoroacetate in the Liver of a Frog

Many workers found that the poisoning animals with sodium fluoroacetate led quickly to a marked increase of citrate in the various tissues, but it failed to find such result in the liver in vivo as well as in vitro. In the liver of a frog, however, an accumulation of a large amount of citric acid was found 6 hours after the poison was orally administered to the animal. To decide whether the accumulation of citric acid in the liver of a frog is due to the formation of fluorocitrate in the liver itself or to the transport of fluorocitrate formed in other organs into the liver, we carried out the experiments using the mitochondrial particles prepared from a frog liver. And it was found that the oxygen uptake of mitochondria was inhibited and that the citrate synthesis of the particle increased by the addition of fluoroacetate with pyruvate and malate as substrates.

Partial Purification and Properties of Phosphoenolpyruvate-carboxykinase from Castor Bean Endosperm

貯蔵物質の異なる発芽種子について, PEP〓OAA反応を触媒する酵素を検索し,ヒマではPEPCK,大豆,エンドウではPEPCが存在することを認め,このうちPEPCKについて精製およびその性質を調べた. ヒマPEPCKは暗所, 30°Cで発芽3日目から活性が認められ,以後急激に増加し7日目にピークを示したので, 7日目の胚乳から酵素を部分精製し,その諸性質を検討した.本酵素はアデニンヌクレオチドに特異的で,活性にMnイオンを必要とする.最適pHはOAA生成反応で6.4, PEP生成反応で8.4であった.また,酵素は解離会合を起こしやすいと推定され, PEP生成反応では, OAA, ATPの飽和曲線がS字型になり,さらに酵素濃度により活性の現われ方も異なる.以上のことから, PEP生成反応に影響する主因子は酵素濃度と基質濃度であると考えられる. 本研究を遂行するに当り,ヒマ種子をご寄贈いただきました伊藤製油株式会社に厚く感謝いたします.

Studies on Isocitrate Lyase of the Germinating Castor Bean Endosperm

ヒマ種子を暗所,30°で発芽させ,胚乳のICL活性変化を測定した.活性は主として可溶性分画に存在し,その分画のICL活性は発芽とともに次第に強まり, 5日目頃に最高に達し,以後急激に弱まる.胚乳の可溶性分画よりICLを分離精製し,その物理化学的性質を検討した.クエン酸, α-ケトグルタル酸はICL活性に対して影響をおよぼさないが,グルコース-6-燐酸は基質に対して不拮抗型阻害剤として作用する.以上の実験結果,ならびに前報の実験結果よりIDH, ICL活性の中間代謝物による代謝調節機作に関して考察を試みた.

Respiration and Carbohydrate Metabolisms of Potato Tuber Part II

When a potato tuber is cut into slices, the activity of dehydrogenase system linked to DPN decreases but the activities of tyrosinase system and G-6-P dehydrogenase increase in the slices. Accompanying the changes of these enzymatic activities, the metabolic pathway in the slices turns from glycolytic path to pentose phosphate path. Tyrosinase oxidizes phenols which are formed from an intermediate of the pentose phosphate path, sedo-heptulose via shikimate as in microorganisms, resulting in increase in the oxygen uptake of the slices. It seems impossible to play a role as a terminal oxidase linked to diphosphopyridine nucleotide.

Studies on Amino Acids

1. Polarographic measurements show that the relationship between pH and the half-wave potential of glycinate, alaniate, aspartate, glutamate and histidinate complexes of copper (II) was in good agreement with theoretical one in all pH range except below about pH 4. 2. The composition of the cupric complexes of all of the amino acids studied was CuA2, where A is the amino acid ion, in the presence of excess amino acid ion, 3. The pKa of the amino acid corresponds to the pH at the intersection point of two straight lines from the equations modified by us, and has been obtained satisfactorily from the experimental results, 4. Discussions has been made on the equations from which dissociation constants for the complex ions can be calculated, The dissociation constants which are obtained by the equation. we used are in good agree-ment with those reported previously by several authors.

Paper Partition Chromatography of Amino Acids

Lutidine (2, 6-dimethylpyridine) was used as a solvent for the separation of copper salts on paper partition chromatograph method, for this is superior to other solvents (phenol, isoamyl alcohol, . n-butanol, s-collidine). As the result of this experiment, the Rf values of copper salts increased with the rise of temperature, and the separation was not completed. The desirable temperature is 18_??_20°C. For making the samples, insoluble copper salts were dissolved in pyridine, in that case, pyridine did not affect the Rf values of copper salts. The Cu-pyridine gave an obscure spot which was separated from the amino acids (copper salts). The contents of water in lutidine influenced the Rf values of copper salts considerably, so it is desirable to saturate lutidine with water completely.