The chromo-peptide phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-D-Arg serves as substrate for the determination of the collagenase units according to Wünsch (1). Collagenase catalyses the hydrolysis of the peptide, the resulting fragment phenylazobenzyloxycarbonyl-Pro-Leu can be detected spectrophotometrically.
A unit according to Wünsch is defined as the turnover of 1 µmole of the substrate per minute at 25 °C and a pH of 7.1.

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