Coproporphyrin Formation in Yeast

IN recent articles in Nature , Keilin 1 has described the occurrence of hæmoglobin, in very low concentration, in certain strains of bakers' yeast, and Keilin and Tissières 2 have likewise demonstrated the presence of hæmoglobin in the mycelia of the moulds Neurospora crassa and Penicillium notatum . In the latter investigation, free protohæm was also found, especially in fragments of mycelium undergoing autolysis, following their projection from the aerated nutrient on to the walls of the containing vessel. The free hæm in the moulds appeared to originate from intracellular hæmoglobin and from some components of cytochrome by an enzymic degradation which accompanied the autolysis of the mycelium. In old mycelia, the free hæm itself was further degraded with liberation of iron and the formation of free porphyrin. These important findings are particularly relevant to the study of porphyrin formation in autolysing yeast.