1962 Volume 51 Issue 5 Pages 335-344
In the course of studies to clarify the metabolic pathways of L-leucine by Proteus vulgaris, a decarboxylase was found which catalyzed the decarboxylation reaction of α-ketoisocaproate to produce isovaleroaldehyde.
Some of the properties of this decarboxylase were examined. It was probable that the enzyme did not require any metal ions for its activity and the activity of the decarboxylase was found to be maximal at pH 5.0. Optimal substrate concentration was above 1×10-2M and one-half of maximal activity was found at the concentration of 1.5×10-3M.
It was also found that the enzyme was considerably stable to aging and against heattreatment, i. e. about 60 per cent of its activity remained by the treatment at 60°C for 5 to 30 minutes.
The decarboxylase did not act on α-ketoglutarate and pyruvate even when thiamine pyrophosphate and magnesium ion were added or the reaction was carried out at pH 6.0. The decarboxylation reaction was inhibited almost completely by p-chloromercuriben-zoate at the concentration of 5×10-5M andd sodium arsenite at the concentration of 1×10-2M.
The author wishes to express his sincere thanks to Prof. S. Usami for his valuable advices throughout the course of this work.