BIOSYNTHESIS OF PHYTOENE FROM ISOPENTENYL PYROPHOSPHATE BY A NEUROSPORA ENZYME-SYSTEM

An enzyme system catalyzing the conversion of isopentenyl pyrophosphate to phytoene has been isolated from Neurospora crassa mycelia. This enzyme system shows an absolute requirement for Mg-, but no other cofactors. Cultures of N. crassa exhibit a low level of phytoene synthesizing activity when grown in the dark. A 2-min in vivo blue light irradiation results in a ninefold increase in activity after 24 h. This increase is dependent on the duration of the light treatment and is inhibited by cycloheximide. A similar blue light-induced elevation of phytoene synthesizing activity was demonstrated in an albino-1 mutant. This enzyme activity was not found in either dark-grown or irradiated cultures of an albino-2 or an albino-3 mutant. © 1979.