Photoregulation of carotenoid biosynthesis in mutants of neurospora crassa: Activities of enzymes involved in the synthesis and conversion of phytoene

Abstract

Synthesis of carotenoids is photoregulated in m any fungi including Neurospora crassa. In order to investigate the regulatory mechanism at the enzyme level, several carotenoid mutants of Neurospora were used to determine the activities of enzymes involved in the carotenoid bio synthetic pathway after growth under illumination or in darkness. Light stimulation of carotenoid form ation was due to enhanced activities of three subsequent enzymes, geranylgeranyl pyrophosphate synthase, phytoene synthase, and phytoene desaturase indicating a coordinated regulation at the enzyme level. Farnesyl pyrophosphate synthase and lycopene cyclase were not involved in light regulation. Im munological studies showed that in the case of phytoene desaturase higher activity in the light originated from an increased amount of this enzyme in light-grown cultures. © 1993, Walter de Gruyter. All rights reserved.