Tadakatsu Kato

Tsuneo Yamane; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui

Abstract The substrate stereospecificity of a dioldehydrase requiring DBC-coenzyme was investigated with d (−)- and l (+)-propanediols as the substrates. Both isomers could be converted to propionaldehyde, but the d -isomer was 1.5–2 times more reactive than the l -form. An inhibition was observed if a high concentration of the l -form or the dl -form was used; moreover, the reactivity of the d -form was depressed by the simultaneous addition of the l -form.

Ryo-Hei Yamada; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui

Abstract 1. 1. When cyanocobalamin or 8-aminocobyrinic acid- c -lactam were heated in 30% NaOH at 120° for 1 h, a green substance was formed whose spectrum was similar to that of vitamin B 12s , and this substance readily reacted with emtyyl iodide to yield cobalt-methyl-8-aminocobyrinic acid- c -lactam as the main product. 2. 2. Cyanocobalamin heated anaerobically in 0.4% NaOH at 100° for 10 min gave a yellow-brown substance whose spectrum ws similar to that of vitamine B 12r , and this substance reacted with methyl iodide of n -butyl bromide to yield cobalt-methyl or cobalt- n -butyl derivatives of dehydrocobalamin, respectively, and their mono- to tricarboxylic acid derivatives. 3. 3. On being heated anaerobically in 0.4% NaOH, cyanocobalamin and aquo(or hydroxo)-cobalamin rapidlyturned yellow-brow, while cyanodehydrocobalamin and aquo(or hydroxo)-dehydrocobalamin changed only verly slowly. From these facts it seems probable that the occurrence of the yellow-brown state with the behaviour of vitamin B 12r may be due to the reduction of the cobalt atom accompanied by dehydrogenation on the B ring of the corrin nucleus. 4. 4. The formation of the green substance from 8-aminocobyrinic acid- c -lactam on vigorous alkali treatment is, however, interpreted by assuming another reaction mechanism causing further reduction of the cobalt atom.

Ryo-Hei Yamada; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui

Ryo-Hei Yamada; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui

Saburo Fukui; Yoshikuni Tamao; Tadakatsu Kato; Toshio Takahashi; Shoichi Shimizu

Saburo Fukui; Shoichi Shimizu; Tadakatsu Kato; Toshio Takahashi; Chikahiro Sakazawa

Tadakatsu Kato; Shoichi Shimizu

Ryo-Hei Yamada; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui

Yoshikuni Tamao; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui

Ryo-Hei Yamada; Tadakatsu Kato; Shoichi Shimizu; Saburo Fukui