Sur les relations entre structure polypeptidique et activité Strépogénique. 1. Peptides de la cystine

The authors propose for the characterization of strepogenic substances of known composition the specific activity, i . e . the number of W OOLLEY units per μmole. Starting from L ‐leucyl‐ L ‐cystinyl‐ L ‐leucyl‐ L ‐valyl‐ L ‐glutamic acid (of very high strepogenine activity, 400 W OOLLEY units per mg, 230 W OOLLEY units per μmole) seven peptides have been synthesized by suppression and/or replacement of amino acid residues. A study of the relation between activity and structure of these peptides shows that: In this group cystine is an indispensable element for activity. This amino acid must either be linked on each side to leucine residues or linked by its carboxyles to leucine, its amino groups being free. From these results, the conception emerges that the strepogenine polypeptides may be characterized by an amino acid (in this group of peptides, cystine) which must be linked to particular amino acid residues. If this conception is correct, there should exist several types of strepogenines depending on the nature of the amino acid essential for their activity.