Growth factors for Corynebacterium diphtheriae. 4. Preparation from yeast

Abstract
The prepn. is described of a concentrate from brewer''s yeast which contains essential growth factors for certain strains of C. diphtheriae gravis. The activity of the whole prepn. is associated with 4 of the 12 ninhydrin-posi-tive components. Most of the activity is associated with an amino-acid, S1, and a peptide, P1, while a 2d amino-acid, S2, and another peptide, P2, have slight activity. The peptide P2 consists of serine, glycine and glutamic acid. A number of synthetic glutamic acid peptides also have activity as growth factors for C. diphtheriae.
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