METHOD FOR ANALYSIS OF L-METHIONINE IN BIOLOGICAL SAMPLE USING FUNCTION-MODIFIED PHENYLALANINE DEHYDROGENASE

摘要

Disclosed is a method for the analysis of L-methionine contained in a sample, which comprises the steps of: subjecting the sample to a treatment that enables the conversion of at least a part of a branched amino acid into an oxo acid; incubating the treated sample together with a modified phenylalanine dehydrogenase and a reaction solution containing resazurin, diaphorase and reduced nicotinamide adenine dinucleotide (NAD<SUP>+</SUP>); and detecting the color developed in the reaction solution after the incubation. Also disclosed is a method for reducing the amount of a branched amino acid in a sample, wherein the branched amino acid is one that is often contained in a test sample for the analysis of L-methionine, and which comprises the step of converting at least a part of the branched amino acid into an oxo acid. It becomes possible to provide a highly sensitive and convenient method for the analysis of L-methionine contained in a sample by using a modified phenylalanine dehydrogenase having the substrate specificity for L-methionine and also provide a method for reducing measurement errors caused by an amino acid other than L-amino acid occurring in a blood sample.