PHYSICOCHEMICAL AND IMMUNOLOGICAL COMPARISONS BETWEEN ANGIOTENSIN I-CONVERTING ENZYMES PURIFIED FROM DIFFERENT MAMMALIAN-SPECIES

Angiotensin I-converting enzyme (ACE) was purified from lungs of pig, rat, monkey and human for comparison of its physicochemical, enzymatic and immunological properties. The protocol involved three chromatogra phic steps after detergent extraction, i.e. DEAE-Spherodex ion exchang e, lisinopril-Sepharose affnity and Superose 12 HPLC, plus Mono-Q HPLC for monkey ACE. Purified ACE's presented numerous homologies: in part icular, closely similar specific activities, catalytic efficiencies, K -m's, optimal pH and chloride activations; the molecular weights were about 170 kDa by SDS-PAGE and 320 kDa by gel-filtration on Superose 12 ; the isoelectric points were about 4.5-4.7. Specific polyclonal antib odies recognized the antigen (porcine ACE) as well as Pat, monkey and human ACEs. In contrast, three monoclonal antibodies (F02.4.1, F01.1.3 and F03) produced against porcine ACE showed some differences: they o nly reacted with pig enzyme and only one (F02.4.1) was anticatalytic. Moreover, the cross-reactivity judged on ELISA with porcine ACE charac terized different epitopes specific for the porcine enzyme. In particu lar, the binding of F02.4.1 was not diminished by previous treatment w ith saturating concentrations of synthetic competitive ACE inhibitors. Thus, the extrapolation to human of data obtained on animal models sh ould be possible at least for pharmacological and medical trials.