Cells of Saccharomyces carlsbergensis 4228 grown aerobically with added
thiamine (1 microgram . ml-1) in a
vitamin B6-free medium contained no detectable
heme precursors, such as delta-aminolevulinate,
coproporphyrin III, or
protoporphyrin IX. The deficiency in
heme precursors in the
thiamine-grown cells was accompanied by previously reported phenomena, i.e., growth depression,
vitamin B6 deficiency, and respiratory deficiency due to a marked decrease in the activities of
heme-containing
enzymes and
cytochrome level (I. Nakamura et al., FEBS Lett. 62: 354-358, 1976). It has been reported that all of the effects of
thiamine are abolished by adding
pyridoxine to the medium. delta-Aminolevulinate was found to have quite similar effects to those of
pyridoxine, except that growth was partially improved by delta-aminolevulinate, whereas it was fully restored by
pyridoxine. Incubation of the
thiamine-grown cells with delta-aminolevulinate resulted in the appearance of the
heme precursors and the
heme-containing
enzymes. Consistent with the lowered amount of
vitamin B6, the
thiamine-grown cells had a lowered activity of
delta-aminolevulinate synthase, a
pyridoxal phosphate-dependent
enzyme. Not only the
holoenzyme activity but also the
apoenzyme activity was very low in these cells. These results indicate that the
thiamine-induced
vitamin B6 deficiency brings about the decrease in
delta-aminolevulinate synthase activity, which leads to
heme deficiency and therefore to respiratory deficiency.