Neokyotorphin formation and quantitative evolution following human hemoglobin hydrolysis with cathepsin D.

In vitro human hemoglobin hydrolysis by cathepsin D was investigated. The quantitative evolution of neokyotorphin following the hydrolysis was determined by high-performance liquid chromatography coupled with a photodiode array detector. Spectral comparisons allowed us to identify neokyotorphin in the hydrolysates all along the hydrolysis. Second order derivative spectrometry was used in order to verify the presence of tyrosine in the peptide. This provided informations about the mechanism of cathepsin D activity towards hemoglobin. Moreover it confirmed that hemoglobin could appear as a precursor of some bioactive peptides following proteolytic degradation.