Angiotensin converting enzymes from human urine of mild hypertensive untreated patients resemble the N-terminal fragment of human angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE) activity was analyzed in human urine collected from mild hypertensive untreated patients. DEAE-cellulose chromat ography using linear gradient elution revealed two forms of angiotensin I-c onverting enzyme, eluted in the conductivity of 0.75 and 1.25 mS. The fract ions of each conductivity were pooled and submitted to direct eel filtratio n in an AcA-34 column, and the apparent molecular weights of urinary ACEs w ere estimated as 90 kDa (for ACE eluted in 0.75 mS) and 65 kDa (for ACE elu ted in 1.25 mS). Both enzymes have a K-i of the order of 10(-7) M for the s pecific inhibitors studied, and are able to hydrolyze luteinizing hormone-r eleasing hormone and N-acetyl-Ser-Asp-Lys-Pro as described for N-domain ACE . By Western blot analysis, both peaks were recognized by ACE-specific anti body Y4, confirming the molecular weight already described. A plate precipi tation assay using monoclonal antibodies to the N-domain of ACE showed that both forms of ACE binds with all monoclonal antibodies to the active N-dom ain ACE, suggesting that these forms of human urine ACEs resemble the N-fra gment of ACE. The HP2 ACE (65 kDa) is similar to low molecular weight (LMW) ACE from normal subjects, and the HP2 ACE (90 kDa) is different from high molecular weight (190 kDa) and LMW (65 kDa) normal ACEs. The 90 kDa ACE cou ld have an important role in development of hypertension. It will be fundam ental to elucidate the molecular mechanism responsible for the genesis of t his isoform. (C) 2001 Elsevier Science Ltd. All rights reserved.