Mass spectrometry methods for simultaneous detection of metabolic enzyme activity and metabolite levels

Abstract

The present invention provides a method for detecting a metabolic disorder in an individual. The method involves (a) contacting a sample containing (i) one or more metabolically indicative enzymes and (ii) one or more metabolic analytes, with one or more substrates for said one or more enzymes to produce a reaction admixture, under conditions in which at least one of said enzymes is capable of acting on a corresponding substrate to generate at least one product; (b) contacting said reaction admixture with a reagent that inhibits the ability of said one or more enzymes to act on a corresponding substrate, wherein said one or more metabolic analytes and said at least one product are soluble in said reagent; to produce a test sample and (c) determining the presence or amount of said one or more metabolic analytes and said at least one product contained in said test sample using mass spectrometry, wherein a determined presence or amount of said one or more metabolic analytes and said at least one product correlates with presence or absence of said metabolic disorder.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates generally to diagnostic medicine and more specifically to methods for diagnosing metabolic disorders. [0002] Metabolism is the process of building the body's molecular structures from nutrients (anabolism) and breaking them down for energy (catabolism). Metabolic processes result in growth, produce energy, eliminate wastes, and control distribution of nutrients in the body. Homeostasis, or a steady state, in the body is a result of normal metabolism. [0003] Enzymes play an important role in metabolism because they catalyze conversion of one molecule to another during metabolic processes. When a metabolic enzyme is faulty or present in an abnormal amount in an individual, a metabolic disorder can result. Metabolic disorders are frequently due to genetic inheritance that leads to absence or overproduction of an enzyme or production of a faulty enzyme. [0004] As an example, deficiencies produced by an inactive gene can pr...

AI Technical Summary

Problems solved by technology

When a metabolic enzyme is faulty or present in an abnormal amount in an individual, a metabolic disorder can result.

Such an enzyme deficiency typically prevents normal metabolism of a nutrient, causing the nutrient or its metabolite to build up in the body to toxic levels.

An enzyme deficiency can also cause nutrient deficiencies when an enzyme is unable to make a normal end-product of a metabolic process.

Nutrient deficiencies resulting from metabolic disorders can lead to impaired growth and development, and other severe health problems.

Many inherited metabolic disorders are fatal in the first weeks or months of postnatal life, for example, severe defects in the conversion of pyruvate to acetyl coenzyme A (CoA), some urea cycle defects, and severe defects in the processing of fructose.

Unfortunately, newborns are not typically screened for other metabolic disorders such as homocysteinuria, maple syrup urine disease, organic acid disorders, and disorders of fatty acid oxidation.

As a result, these disorders are often detected in infants and children after damage has occurred and effects such as developmental delay and mental retardation become apparent.

Wide-spread newborn testing for multiple inherited metabolic disorders has been unavailable due, in part, to cost associated with each test.

However, development of multi-enzyme / metabolite testing has been hindered by the different conditions needed for enzyme tests in comparison to metabolite tests.

Currently, enzyme and metabolite tests cannot be carried out simultaneously from a single patient sample.

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