ENZYMATIC CYCLING ASSAYS FOR HOMOCYSTEINE AND CYSTATHIONINE

摘要

The present invention provides an enyzmatic cycling assay for assessing the amount of homocysteine and/or cystathionine in a solution such as blood, blood derivatives, or urine. The assay comprises the steps of contacting the solution containing homocysteine and/or cystathionine to form a reaction mixture, with CBS, or derivative thereof, L-serine, and CBL or a derivative thereof for a time period sufficient to catalyze the cyclical conversion of homocysteine to cystathionine and the reconversion of cystathionine to homocysteine with the production of pyruvate and ammonia and determining the amount of homocysteine and/or ammonia present in the reaction mixture. Expression vectors, isolation procedures for CBS, or derivative thereof, L-serine and CBL or derivative thereof and test kits for carrying out the assay are provided. Figure (1) depicts absorbance versus time plots obtained using aqueous solutions of pyruvate (5-100UM) demonstrating the quantitation of pyruvate.