Abstract: Disclosed is a method for quantifying L-tryptophan involving a step for mixing a specimen, L-tryptophan oxidase, and water, a step for allowing the obtained reaction solution to stand a predetermined period of time in the presence of oxygen, and a step for measuring the reaction product resulting from action of enzymes present in the reaction solution after allowing to stand. The L-tryptophan oxidase has a given amino acid sequence and has oxidase activity that generates hydrogen peroxide and ammonia by acting on the L-tryptophan in the presence of oxygen and water. The oxidase activity of the L-tryptophan oxidase on the L-phenylalanine is in the range of 0-3% of the oxidase activity thereof on the L-tryptophan, and the L-tryptophan oxidase does not have oxidase activity on protein-constituting amino acids other than L-tryptophan and L-phenylalanine. Also disclosed are a kit used to quantify the L-tryptophan containing L-tryptophan oxidase, and an enzyme sensor using the L-tryptophan oxidase.

Abstract: There is provided a method for quantifying a subject substance, of which typical examples are amino acids. The method of the present invention comprises the following steps: the step of allowing an enzyme that can generate pyrophosphate by using adenosine triphosphate (ATP) as a substrate with converting the subject substance to act on the subject substance to generate pyrophosphate; the step of allowing pyruvate pyrophosphate dikinase (PPDK) to act on the generated pyrophosphate in the presence of adenosine monophosphate (AMP) and phosphoenolpyruvate (PEP) to generate ATP, phosphoric acid, and pyruvate; and the step of quantifying the generated pyruvate, and amount of the subject substance is determined on the basis of the obtained amount of pyruvate. According to the present invention, an amino acid in a biological sample containing a lot of various kinds of contaminants such as inorganic phosphoric acid and urea can be conveniently and quickly quantified without being influenced by the contaminants.

Abstract: Disclosed is a method for quantifying L-tryptophan involving a step for mixing a specimen, L-tryptophan oxidase, and water, a step for allowing the obtained reaction solution to stand a predetermined period of time in the presence of oxygen, and a step for measuring the reaction product resulting from action of enzymes present in the reaction solution after allowing to stand. Also disclosed are a kit used to quantify the L-tryptophan containing L-tryptophan oxidase, and an enzyme sensor using the L-tryptophan oxidase. This method, kit and enzyme sensor use an L-tryptophan-specific enzyme, so are capable of quantifying L-tryptophan even in the presence of other amino acids.

Abstract: There is provided a method for quantifying a subject substance, of which typical examples are amino acids. The method of the present invention comprises the following steps: the step of allowing an enzyme that can generate pyrophosphate by using adenosine triphosphate (ATP) as a substrate with converting the subject substance to act on the subject substance to generate pyrophosphate; the step of allowing pyruvate pyrophosphate dikinase (PPDK) to act on the generated pyrophosphate in the presence of adenosine monophosphate (AMP) and phosphoenolpyruvate (PEP) to generate ATP, phosphoric acid, and pyruvate; and the step of quantifying the generated pyruvate, and amount of the subject substance is determined on the basis of the obtained amount of pyruvate. According to the present invention, an amino acid in a biological sample containing a lot of various kinds of contaminants such as inorganic phosphoric acid and urea can be conveniently and quickly quantified without being influenced by the contaminants.

Abstract: Disclosed is a method for quantifying L-tryptophan involving a step for mixing a specimen, L-tryptophan oxidase, and water, a step for allowing the obtained reaction solution to stand a predetermined period of time in the presence of oxygen, and a step for measuring the reaction product resulting from action of enzymes present in the reaction solution after allowing to stand. The L-tryptophan oxidase has a given amino acid sequence and has oxidase activity that generates hydrogen peroxide and ammonia by acting on the L-tryptophan in the presence of oxygen and water. The oxidase activity of the L-tryptophan oxidase on the L-phenylalanine is in the range of 0-3% of the oxidase activity thereof on the L-tryptophan, and the L-tryptophan oxidase does not have oxidase activity on protein-constituting amino acids other than L-tryptophan and L-phenylalanine. Also disclosed are a kit used to quantify the L-tryptophan containing L-tryptophan oxidase, and an enzyme sensor using the L-tryptophan oxidase.