High specificity homocysteine assays for biological samples

Abstract

Novel enzymatic methods to determine the concentration of homocysteine in biological fluids are described. In a typical embodiment of the invention, the biological fluid sample is from a patient, and the methods of the invention are useful to assess risk for cardiovascular disease. The novel methods of the invention involve use of particular homocysteinase enzymes that permit the determination of homocysteine concentrations in biological samples without interference from the concentrations of cysteine and/or of methionine that are routinely present in such samples. There is also provided a diagnostic kit for use in determining the amount of homocysteine in a biological sample comprising (a) a homocysteinase having the aformentioned characteristics, and (b) at least one reagent capable of being used to determine the amount of product formed in the homocysteinase reaction. In a further aspect, the homocysteinase is provided as a chimeric molecule that comprises amino acid subsequences derived from, or patterned on, more than one homocysteinase, and which is typically produced from a chimeric polynucleotide that encodes therefor. Additional enhancements in homocysteine assay methodology include use of the enzyme .gamma.-glutamylcysteine synthetase to further limit any interference from cysteine present in the biological samples.

Dependencies are inferred from the claim text.