Purification and identification of a yellow pteridine characteristic of the larval colour of the kiuki mutant of the silkworm,Bombyx mori

A yellow pteridine characteristic of the Kiuki mutant of the silkworm Bombyx mori was isolated from the larval integument by successive column chromatography systems consisting of ECTEOLA-cellulose, P-Sephadex, and Sephadex G-25. Based on mass spectra, the IR spectrum, ORD spectrum and degradation experiments, the chemical structure of the yellow pigment was established as 7,8-dihydro-6-(l)-lactyllumazine sepialumazine. The compound has been found to be present in the integument of other strains of Bombyx mori. The yellow colour of the Kiuki larvae is caused by sepialumazine accumulation in the integument. Both sepiapterin deaminase and sepiapterin reductase were assayed in mutant Kiuki, mutant lemon and normal type silkworms. A higher activity of sepiapterin deaminase was found in the Kiuki mutant than in normal silkworms. The accumulation of sepialumazine in Kiuki larvae may be due to the high activity of this enzyme.