SPECTROPHOTOMETRIC DETERMINATION OF L-LYSINE CONCENTRATION USING L-LYSINE ALPHA-OXIDASE FROM TRICHODERMA SP AND 3,3',5,5'-TETRAMETHYLBENZIDINE DIHYDROCHLORIDE

A simple and relatively sensitive procedure was developed for determination of L-lysine at 3-30 mmole/L concentration. The procedure does not involve the carcinogenic compound o-dianisidine. L-lysine alpha-oxidase catalyzed oxidative deamination of L-lysine with O2 consumption and formation of H2O2, NH3 and alpha-keto-epsilon-aminocapronic acid. Horseradish peroxidase and a non-carcinogenic compound 3,3,5,5'-tetramethylbenzidine dihydrochloride as an electron donor were used in determination of H2O2 formed. The procedure developed enabled also to measure the L-lysine alpha-oxidase activity at the enzyme concentrations of 10-500 ng/ml. The only limitation of the procedure is relatively low pH-values of the reaction medium.