bifunctional enzyme from Bacillus subtilis which catalyzes second & third steps in biosynthesis of riboflavin; deamination of 2,5-diamino-6-ribosylamino-4(3H)- pyrimidinone 5'-phosphate and reduction of 5-amino-6- ribosylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate