NT5E and hyperinsulinemic hypoglycemia, familial, 4: These results indicate that the presence of FAD and FMN in the medium did not lead to efficient uptake of vitamin B2 into GPI-deficient cells; this is because FAD and FMN were inefficiently hydrolyzed to FMN and RF, respectively, because of the defective expression of CD73 and ALP; this resulted in intracellular vitamin B2 deficiency.