Peptide substrates for chymosin (rennin): conformational studies of kappa-casein and some kappa-casein-related oligopeptides by circular dichroism and secondary structure prediction.

Circular dichroism spectra of a series of synthetic, kappa-casein-related oligopeptide substrates for chymosin in water and in surfactant solution were determined. The results show that there is a good correlation between the beta-structure forming potential of these peptides as found by using structure-predictive methods and the conformation in dilute sodium dodecyl sulfate solutions. The results support earlier suggestions concerning enzyme-substrate interaction which were made on the basis of X-ray analysis of acid proteinases. A predicted secondary structure of the whole kappa-casein molecule obtained by using a combination of three methods is also presented.