Abstract: The effects of vitamin B₆ (VB₆) deficiency on the amino acid metabolism, fatty acid metabolism and aminotransferase activity of the silkworm, Bombyx mori, were studied in newly ecdysed 5th instar larvae reared on a semisynthetic diet that contained no mulberry powder and in which vitaminfree casein was the protein source. Under VB₆deficient conditions, larval growth was retarded, the catabolism of branched chain amino acid (leucine, valine, isoleucine) was inhibited, and lysine catabolism was stimulated. The leucine, valine, isoleucine and serine content in haemolymph were markedly increased by VB₆ deficiency. Conversely, lysine, proline, arginine, methionine and glutamine content decreased, especially markedly in lysine. The lack of dietary VB₆ also inhibited synthetic metabolism of fatty acids and reduced the activity of glutamic pyruvic transaminase.

Key words: Bombyx mori, semisynthetic diet, vitamin B₆ deficiency, metabolism of amino acid and fatty acid