Sensitive, optimized assay for serum AMP deaminase.
A sensitive, optimized assay for serum AMP deaminase (EC 3.5.4.6) is presented, which is based on a colorimetric indophenol determination of ammonia liberated during the enzyme reaction. An average enzyme activity in serum of 2.7 U/liter (n = 36, range 0-6.2) for healthy adults was established. Both the enzyme and colorimetric reactions were optimized to give an assay sensitivity of 0.2 U/liter of serum, a 98-99% analytical recovery in the normal serum enzyme concentration range, and a CV of 7.9% in-run and 10.6% between-run. This optimization included studies on specific buffer, pH, ionic strength, and potential activators. The Km for the enzyme in serum was determinated to be 1.4 X 10(-3) mol/liter, which agrees well with the value reported for human skeletal muscle enzyme. Above-normal serum AMP deaminase activity may be present in various myopathies and could be useful in detecting carriers of the X-linked dystrophies.
D000659:AMP Deaminase / Q000097:blood*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000328:Adult; D004355:Drug Stability; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008832:Microchemistry; D009136:Muscular Dystrophies / Q000175:diagnosis; D009709:Nucleotide Deaminases / Q000097:blood*; D009994:Osmolar Concentration; D010744:Phosphoric Monoester Hydrolases / Q000097:blood; D012737:Sex Factors
D000255:Adenosine Triphosphate; D010744:Phosphoric Monoester Hydrolases; D009709:Nucleotide Deaminases; D000659:AMP Deaminase