[The activity of enzymes involved in synthesis and hydrolysis of flavin adenine dinucleotide is Pichia guilliermondii studies at different levels of flavinogenesis].

The activity of FAD-pyrophosphorylase and FAD-hydrolase (nucleotidepyrophosphatase) was studied in extracts of Pichia guilliermondii ATCC 9058 capable of riboflavin over-production. The specific activity of the enzymes was highest at the logarithmic growth phase (2.6 and 3.8 mcmoles of FAD per 1 min per 1 mg of protein X10(-5), respectively), and did not increase upon the induction of riboflavin overproduction. A decrease in the content of hemin compounds and a low content of flavins in the cells of Pichia guilliermondii mutants had no considerable effect on the activity of the two enzymes. When the yeast was cultivated on a medium containing hexadecane, an increase in the content of FAD in the cells was not accompanied with a rise in the activity of FAD-pyrophosphorylase. The activity of the enzyme did not change when succinate and lactate, the substrates of FAD-containing enzymes, were used as the source of carbon. The activity of FAD-pyrophosphorylase increased only when iron-deficient cells of the yeast were grown or incubated on a medium containing glycine; this stimulation was inhibited by cycloheximide.