Mechanism of Photoregulated Carotenogenesis inRhodotorula minutaV. Photoinduction of 3-Hydroxy-3-Methyl Glutaryl Coenzyme A Reductase

摘要

The effect of light on the activity of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase inRhodotorula minutawas studied in cell-free extracts prepared from cells grown under various light conditions.HMG-CoA reductase activity in cells grown under continuous illumination was higher than that in cells grown in the dark, and depended on the light intensity used during incubation. The relationship between activity A (nmol/mg-N/min) and light intensity I (erg/cm2/sec) was expressed by the equation A=0.72 log I$0.80.Illumination at−1.5°C followed by dark incubation at 26°C resulted in a rapid increase in HMG-CoA reductase activity immediately after the beginning of incubation. This photoinduced HMG-CoA reductase activity was regulated by the light dose and followed the Roscoe-Bunsen reciprocity law.When cycloheximide was added immediately after the beginning of incubation in the dark, the increase in HMG-CoA reductase activity was completely inhibited. The inhibitory effect of cycloheximide, however, gradually decreased with the delay of the addition.On the basis of these results we have postulated that the photoregulation of carotenogenesis inRh. minutaresults from the photoregulation of HMG-CoA reductase synthe