Distribution and properties of flavokinase in the developing chick embryo.

1. Localization of flavokinase was studied in the nonembryonic portions of the chicken egg, in embryos at various stages of development, and in the adult hen. 2. Embryonic biosynthesis of flavin nomonucleotide (FMN) increases with increasing protein synthesis. 3. In the embryo, higher activity of flavokinase was observed in intestine, heart, liver, and yolk sac. 4. Lower activity was observed in allantoic membrane and fluid. 5. No significant activity was measured in yolk. 6. Both specific and total flavokinase activities in organs of the more aerobic and metabolically active adult chicken are considerably greater than those of embryo organs. 7. Flavokinase from embryonic liver was enriched by affinity chromatography by using N-10-flavinyl agarose. 8. The partially purified enzyme has properties generally similar to other animal flavokinases.