Kinetic study of the appearance of an anti-bacterial peptide in the course of bovine haemoglobin peptic hydrolysis
Résumé
The kinetics of the α (1-23) peptide, which is the first anti-bacterial peptide to be isolated from a haemoglobin hydrolysate, was studied in the course of peptic hydrolysis at pH 4.5 and 23 mC in an homogenous-phase system. A one-step reversed-phase HPLC coupled with photodiode array detector method was applied to identify and isolate this anti-bacterial peptide. The kinetics of peptide appearance were investigated in acetate buffer alone and in urea as a haemoglobindenaturing agent. Two different mechanisms, ' one-byone ' for native haemoglobin hydrolysis and ' zipper ' for denatured haemoglobin hydrolysis, were observed. Whatever the haemoglobin state, native or denatured, and whatever the hydrolytic mechanism, one-by-one or zipper, the anti-bacterial α (1-23) peptide is a transient peptide. To prepare the α (1-23) peptide it is suitable to hydrolyse haemoglobin in the presence of urea at a corrected degree of hydrolysis (DH c ) of 13.5 %. The amount of peptide produced in the presence of urea was twice as high as for the hydrolysis of native haemoglobin. The yields of α (1-23) peptide with respect to haemoglobin at the optimal DH c values were 55 and 25 % respectively.
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