Angiotensin-forming enzyme in human brain.

The subcellular and regional distribution of angiotensin-forming enzyme was examined in human brain. A relatively purified form of this enzyme was obtained by discontinuous sucrose density gradient subfractionation of the crude mitochondrial fraction. Of the six brain regions examined, the cerebellar cortex crude mitochondrial fraction had the highest angiotensin-forming enzyme content. Kinetic characteristics, with respect to hog plasma renin and synthetic tetradecapeptide substrates and optimum pH range (4·5–5·5), were similar for both the particulate and soluble forms of the enzyme. Both forms also had a lower affinity for human plasma renin substrate. Different substrate kinetics and optimum pH range were obtained for the brain angiotensin-forming enzyme and kidney renin. Because of its potential clinical implication, a brain renin-angiotensin-aldosterone system, which is independent of kidney and adrenals, merits further study.