Limit of detection: 80% B/B₀: 0.2 nM after 18 hour immunological reaction · Sensitivity: 50% B/B₀: 2.0 nM after 3 hour immunological reaction; 0.5 nM after 18 hour immunological reaction · N-Acetyl Ser-Asp-Lys-Pro (AcSDKP) is a tetrapeptide growth regulatory hormone which inhibits the proliferation of hematopoietic stem cells.¹ The dipeptidase Angiotensin Converting Enzyme (ACE) actively metabolizes circulating AcSDKP, giving it a brief plasma half life of 4 to 5 minutes. ACE inhibition is a major therapeutic end point in the treatment of hypertension management. A further consequence of ACE inhibition is the accumulation of AcSDKP in the plasma and the urine.^2,3 This accumulation may have physiological effects, which are manifested as the anemia of chronic ACE inhibitor toxicity. More commonly, plasma and urine AcSDKP levels can be used as a biomarker of ACE inhibition and an index of patient compliance with therapy.⁴ Measurement of AcSDKP in human urine or plasma can be readily accomplished by enzyme immunoassay.⁵

1 Lenfant, M., Wdzieczak-Bakala, J., Guittet, E., et al. Inhibitor of hematopoietic pluripotent stem cell proliferation: Purification and determination of its structure. Proc Natl Acad Sci USA 86 779-782 (1989).

2 Azizi, M., Ezan, E., Nicolet, L., et al. High plasma level of N-Acetyl-Seryl-Aspartyl-Lysyl-Proline: A new marker of chronic angiotensin-converting enzyme inhibition. Hypertension 30(5) 1015-1019 (1997).

3 Azizi, M., Ezan, E., Reny, J., et al. Renal and metabolic clearance of N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (AcSDKP) during angiotension-converting enzyme inhibition in humans. Hypertension 33(3) 879-886 (1999).

4 Struthers, A.D., MacFadyen, R., Fraser, C., et al. Nonadherence with angiotensin-converting enzyme inhibitor therapy. A comparison of different ways of measuring it in patients with chronic heart failure. J Am Coll Cardiol 34(7) 2072-2077 (1999).

5 Pradelles, P., Frobert, Y., Créminon, C., et al. Negative regulator of pluripotent hematopoietic stem cell proliferation in human white blood cells and plasma as analysed by enzyme immunoassay. Biochem Biophys Res Commun 170 986-993 (1990).

Erdös, E.G. News about ACE, or, the separate lives of 'Siamese Twin' domains. J Clin Invest 97 588 (1996).

Junot, C., Pruvost, A., Créminon, C., et al. Characterization of immunoreactive acetyl-Ser-Asp-Lys-Pro in human plasma and urine by liquid chromatography-electrospray mass spectrometry. J Chromatogr B 752 69-75 (2001).

Azizi, M., Rousseau, A., Ezan, E., et al. Acute angiotensin-converting enzyme inhibition increases the plasma level of the natural stem cell regulator N-Acetyl-Seryl-Aspartyl-Lysyl-Proline. J Clin Invest 97 839-844 (1996).

Pradelles, P., Frobert, Y., Créminon, C., et al. Negative regulator of pluripotent hematopoietic stem cell proliferation in human white blood cells and plasma as analysed by enzyme immunoassay. Biochem Biophys Res Commun 170 986-993 (1990).

Lenfant, M., Wdzieczak-Bakala, J., Guittet, E., et al. Inhibitor of hematopoietic pluripotent stem cell proliferation: Purification and determination of its structure. Proc Natl Acad Sci USA 86 779-782 (1989).

Azizi, M., Ezan, E., Nicolet, L., et al. High plasma level of N-Acetyl-Seryl-Aspartyl-Lysyl-Proline: A new marker of chronic angiotensin-converting enzyme inhibition. Hypertension 30(5) 1015-1019 (1997).

Azizi, M., Ezan, E., Reny, J., et al. Renal and metabolic clearance of N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (AcSDKP) during angiotension-converting enzyme inhibition in humans. Hypertension 33(3) 879-886 (1999).

Struthers, A.D., MacFadyen, R., Fraser, C., et al. Nonadherence with angiotensin-converting enzyme inhibitor therapy. A comparison of different ways of measuring it in patients with chronic heart failure. J Am Coll Cardiol 34(7) 2072-2077 (1999).

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