A modified colorimetric method for the determination of pyrrolidone carboxylyl peptidase activity in bacteria

The direct spectrophotometric estimation of ferrocyanide (1) suggested the possibility of measuring small quantities of reducing sugars. However, as previously described (1), the method is not applicable to the measurement of reducing sugars because of the high temperature required for the required oxidation step.Due to the relative differences in molar extinction coefficients at the wavelengths concerned (1,5), the measurement of ferrocyanide rather than ferricyanide (5) provides a large increase in sensitivity.A comparison of such a method with a modified folin-Wu method (2–4) for estimation of blood glucose should indicate the possibility of its application to biological fluids containing cells and proteins.