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A simple, rapid, highly sensitive and reproducible assay for angiotensin-converting enzyme in untreated serum is described. It is based on the conversion of the substrate analog, hippuryl-L-histidyl-L-leucine (5 mM in 0.1 M K phosphate, pH 8.3-0.3 M NaCl) to hippurate and L-histidyl-L-leucine, which is quantified spectrofluorimetrically (lamdba excitation = 360 nm; lamdba fluorescence = 500 nm) by formation of a fluorescent adduct with ophthaldialdehyde. The chloride requirement and inhibition and activation patterns correspond to those for angiotensin-converting enzyme. The Km for hippuryl-L-histidyl-L-leucine was 1.33 mM. The mean value of serum angiotensin-converting enzyme for 58 normal human subjects (mean age, 32 years; range 19-57) was 32.2 +/- 1.30 (SE), with a standard deviation of 9.87 nmol/min/ml serum. The assay is useful for the diagnosis and possible management of sarcoidosis and may have other applications in the future.
J Friedland, and
E Silverstein
April 1979,
Clinica chimica acta; international journal of clinical chemistry,
J Friedland, and
E Silverstein
July 1983,
Clinical chemistry,
J Friedland, and
E Silverstein
January 2006,
Nature protocols,
J Friedland, and
E Silverstein
September 1984,
Annals of clinical biochemistry,
J Friedland, and
E Silverstein
July 1975,
The Biochemical journal,
J Friedland, and
E Silverstein
July 1978,
Analytical biochemistry,
J Friedland, and
E Silverstein
December 1981,
Clinical chemistry,
J Friedland, and
E Silverstein
June 1982,
Clinical chemistry,
J Friedland, and
E Silverstein
June 1983,
Clinical chemistry,
J Friedland, and
E Silverstein
January 1984,
Clinical chemistry,
