Stimulation of growth and cytochrome P-450 production by high glucose concentration in strains of Saccharomyces cerevisiae: direct relationship of adenosine 3':5'-cyclic monophosphate and cytochrome a + a3 concentrations.

We have noted earlier the inverse relationship between the concentration of the microsomal-fraction-located cytochrome P-450 and the mitochondria1 cytochrome a + a3. These results were in brewer’s yeast grown from slope in media at various glucose concentrations (Wiseman et al., 1975). Similarly, on transfer from 0.5%-glucoseto 20%-glucose-containing media, a rapid fall in the concentration of cytochrome a + a3 was shown to be closely correlated with the sharp rise in the cytochrome P-450 concentration over the first 6-10h of culture (Wiseman & Woods, 1977). Direct addition of cyclic AMP to yeast protoplasts showed a 60% repression of cytochrome P-450 production by the protoplasts being incubated in 5% glucose. Also, it was shown that yeast cyclic AMP concentrations were higher after growth in low-glucose media (Wiseman et al., 1978). The high rate of growth of the yeast in high-glucose media (Wiseman et al., 1975) is associated with a high rate of glycolysis. Activities of many glycolytic enzymes increase greatly in 20%-glucosecontaining medium (Hommes, 1966); these enzymes may also be repressed by cyclic AMP! It should be possible to test this hypothesis directly in yeast protoplasts by addition of cyclic AMP. Cyclic AMP concentrations may also be inversely related to growth rate in yeast, via glucose uptake rate. We now demonstrate the direct relationship of cytochrome a + a3 concentration to cyclic AMP concentration in yeast (N.C.Y.C. 240) grown at various glucose concentrations in complex media (Fig. 1). In addition, another (unrelated) yeast strain (N.C.Y.C. 239) has been found, after the testing of several