[Participation of serine proteinases in transforming the high molecular weight (600 kDa) form of angiotensin 1-converting enzyme into the low molecular weight form (190 kDa)].

A high molecular form of angiotensin-converting enzyme with mol mass about 600 kDa was found simultaneously with the well-known low molecular enzyme form of 190 kDa after fractionation of freshly prepared extracts from bovine kidney cortex and lung tissues by means of ammonium sulfate or gel filtration on Sephadex G-200. The rate of substrate hydrolysis was adequately Cl'-dependent for both these enzyme forms and specific inhibitors nonapeptide SQ 20881 and pentapeptide SQ 20475 inhibited similarly their activity. The enzyme high molecular form transformed into its low molecular derivative after storage, in freezing-thawing and ultrafiltration.

[An endogenous activator of angiotensin-converting enzyme].

An endogenous activator of the angiotensin-converting enzyme (ACE), unknown earlier, was detected in freshly prepared human neutrophils. Supernatants of the neutrophil suspension produced a 1.6-2-fold activation of the ACE isolated from bovine kidney cortex.

Angiotensin-converting enzyme activator from purified human neutrophils.

An endogenous ACE activator has been revealed. Neutrophil-enriched human leucocyte preparations released in isotonic media a relatively thermostable factor, capable of increasing the angiotensin-converting enzyme activity 1.6-2.