Studies on the respiratory enzyme systems in the silkworm egg

(II) Existence of a L-amino acid oxidase and the variation of its activity during the incubation

Abstract

Since little is known about the enzymic oxidation of L-amino acid in the silkworm egg, we have tried to make clear this problem by using L-alanine and L-glutamic acid as substrates.
The results obtained are as follows:
1) In the presence of L-amino acid, NH₃ output by the enzyme solution prepared from silkworm eggs increased with O₂ uptake by the enzyme solution. The molar ratio of NH₃ output: O₂ uptake was nearly 2: 1. This fact suggests that the amino acids are desaminated oxidatively by an oxidase or an oxidase system in the silkworm egg.
2) As it was not until about 1/500 M of potassium cyanide that the activity of the oxidase was almost completely inhibited, the enzyme seems to have relatively strong resistance to the cyanide.
3) The activity of L-amino acid oxidase in the silkworm egg increased gradually till the middle of incubation, and thereafter it decreased towards the hatching. From this, it may be postulated that the oxidase is connected physiologically with the consumption of the yolk.