Which enzyme enables the measurement of creatinine through a coupled reaction with peroxidase?

The measurement of creatinine through a coupled reaction with peroxidase is facilitated by sarcosine oxidase. This enzyme catalyzes the oxidation of sarcosine to produce hydrogen peroxide, which is then utilized in a subsequent reaction with peroxidase. The peroxidase acts on hydrogen peroxide and a chromogen, leading to a color change that can be measured photometrically. This method is valuable in clinical chemistry for determining creatinine levels in the blood or urine, as it provides a reliable and specific means of measurement.

In contrast to sarcosine oxidase, the other enzymes mentioned serve different functions. Glucose-6-phosphate dehydrogenase is involved in glucose metabolism and not in the creatinine measurement process. Creatinine iminohydrolase specifically catalyzes the hydrolysis of creatinine into other metabolites but does not participate in a coupled reaction with peroxidase. Creatine kinase is associated with the reversible conversion of creatine to phosphocreatine and does not directly measure creatinine levels. Thus, sarcosine oxidase is the enzyme that is critical in conjunction with peroxidase for the effective quantification of creatinine.