Chalcone synthase activity, increase

The beginning of secondary product formation is often directly coupled with the synthesis of the corresponding enzymes. One example is the biosynthesis of flavonoids in cell cultures of Petroselinum hortense (Fig. 7). Here the regulatory mechanisms were extensively investigated with phenylalanine ammonia-lyase (PAL) (D 22.2.1) and chalcone synthase (D 22.3.3), the key enzymes of the biosynthetic chain. Experiments with inhibitors of transcription and translation showed that the increase of enzyme activity depends on RNA and protein biosynthesis. Labeling experiments demonstrated that it is caused by an accelerated rate of enzyme synthesis. 

Irradiation with UV seems to stimulate RNA synthesis immediately, but to increase the rate of protein synthesis only after the lag period (Fig. 7) which precedes the increase of enzyme activity. In agreement with these results in vitro translation has shown that the amounts of PAL-mRNA and chalcone synthase-... 

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