Creatine assay by enzymatic conversion to sarcosine - for diagnosis of heart disease, etc.

摘要

Determn. of creatine in body fluids (plasma, serum or urine) is effected by (a) converting the creatine to sarcosine by enzymatic hydrolysis with creatinase (creatine amidinohydrolase; EC 3.5.3.3), and (b) converting the sarcosine to a deriv. whose further reaction produces a change in light absorption. - Step (b) is effected using a system comprising sarcosine oxidase (SO), peroxidase and 4-aminoantipyrine (AA), optical absorption being measured at a wavelength of 500-600nm. - Reaction mixt. comprises 20 U/ml creatinase, 10 U/ml SO, 5 U/ml peroxidase, 0.015 mM K4Fe(CN)6, ascorbic acid oxidase (amt. not specified), 50 mM phosphate buffer, 1 mM TOOS and 0.2 mM AA.