Coproporphyrin formation in yeast

IN recent articles in Nature, Keilin1 has described the occurrence of haemoglobin, in very low concentration, in certain strains of bakers' yeast, and Keilin and Tissieres2 have likewise demonstrated the presence of haemoglobin in the mycelia of the moulds Neurospora crassa and Penicillium notatum. In the latter investigation, free protohaem 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 haem in the moulds appeared to originate from intracellular haemoglobin and from some components of cytochrome by an enzymic degradation which accompanied the autolysis of the mycelium. In old mycelia, the free haem 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.