An
enzyme-coupled colorimetric assay for quantification of urinary
sarcosine was developed. The proposed method is a specific reaction based on
hydrogen peroxide (H2O2) formation via
sarcosine oxidase (SOX). The liberated H2O2 reacts with
Amplex Red in the presence of
horseradish peroxidase (HRP) to produce the red-fluorescent oxidation product,
resorufin, which can be measured spectrophotometrically (OD570). The method was performed in the 96-well microtiter plate. Reaction conditions, such as pH and reaction time were optimized. At the optimum conditions, the limit of detection (LOD) and quantification (LOQ) were found to be 0.7 and 1 µM, respectively. A good linearity was revealed with a coefficient of 0.990. The assay showed no significant interference from
ascorbic acid,
glucose and
bilirubin. In addition, it is extremely specific for
sarcosine rather than other
amino acids. The determination of
sarcosine in human urine displayed high accuracy and good reproducibility. This method is promising to differentiate
prostate cancer patients from healthy subjects according to urinary
sarcosine level. Altogether, this study provides a rapid, simple and specific tool to determine urinary
sarcosine which could be useful for
prostate cancer diagnosis.