BIOCHEMICAL STUDIES ON THE FORMATION OF THE SILKPROTEIN

VII. THE CONVERSION OF GLYCINE TO SERINE IN THE SILKWORM LARVA

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1. To clarify the conversion of glycine to serine in the silkworm, glycine-l-C¹⁴ and glycine-2-C¹⁴ was given per os to the silkworms, and then serine was isolated from the fibroin and the sericin produced by these silkworms. The serine had a comparatively high radioactivity in its molecule.
2. The carbon of the carboxyl group and the carbon-2 atom of glycine are respectively used for synthesis of the carbon of the carboxylic group and the carbon-2 and -3 atom of serine in the silkworm.
3. It was found that glycine is converted to glyoxylic acid in the silk-worm by clarifing the existence of radioactivity in the glyoxylic acid which was isolated from the body fluid of the silkworms to which glycine-l-C¹⁴ was given per os.
4. These facts seem to suggest that serine which is contained in com-paratively high amount in fibroin (15 per cent) and in sericin (30 per cent) is derived not only directly from the serine in the mulberry leaves eaten by silkworm, but also from the serine which was synthesized from the glycine in the silkworm body.