[Angiotensin-converting enzyme in an OAT-octane reversed micelle system: interaction with the matrix]. / Angiotenzinprevrashchaiushchii ferment v sisteme obrashchennykh mitsell AOT v oktane: vzaimodeistvie s matritsei.

Regulation of catalytic activity and intramolecular structure of the bovine lung angiotensin-converting enzyme was studied using reversed micelles in a sodium docusate-water-octane system, which model the enzyme's environment in vivo. The catalytic parameters of monomeric and dimeric forms of the enzyme in the reversed micellar system were evaluated. The catalytic activity of the angiotensin-converting enzyme extracted from bovine lung with Triton X-100 did not depend on the detergent concentration at a constant level of hydration. An artificially hydrophobized form of the angiotensin-converting enzyme was obtained by modifying the enzyme with stearic acid chloride. The modification leads to the dependence of the catalytic activity on the surfactant concentration, which provides evidence that the enzyme interacts with the micellar matrix. The modified enzyme showed a significant increase in catalytic activity in the reversed micellar system.

[Regulation of catalytic activity and supramolecular structure of angiotensin-converting enzyme in reversed micelles of aerosol OT in octane]. / Reguliatsiia kataliticheskoi aktivnosti i nadmolekuliarnoi struktury angiotenzin-prevrashchaiushchego fermenta v obrashchennykh mitsellakh aérozolia OT v oktane.

Regulation of the catalytic activity and the supramolecular structure of the angiotensin-converting enzyme isolated from bovine lungs has been studied in a system of reversed micelles of aerosol OT (AOT) in octane. The curve for the dependence of the enzyme catalytic activity on the degree of the surfactant hydration (micellar size) has two maxima at the hydration degrees of [H2O]/[AOT] 27 and 31. Data from velocity sedimentation suggest that depending on the hydration degree, the angiotensin-converting enzyme occurs in the system of reversed micelles in both monomeric and dimeric forms, the latter being catalytically active. In contrast with aqueous media, in the reversed micelle system the angiotensin-converting enzyme does not require chloride anions for its catalytic activity. In the system of reversed micelles of AOT in octane the holoenzyme is stable, while the apoenzyme rapidly and irreversibly loses its activity. Under these conditions the apoenzyme shows an ability to incorporate the Zn2+ ions into the enzyme active center; however, only in the presence of a substrate or an inhibitor.