The article by Skeeggs, Kahn, and Shumway explores the preparation and function of the hypertensin-converting enzyme. They discovered that hypertensin exists in two forms: hypertensin I, produced by renin, and hypertensin II, which is activated by an enzyme in the plasma requiring chloride ions. Both forms are pressor agents when injected intravenously, but hypertensin II is a potent vasoconstrictor, while hypertensin I is not. The conversion of hypertensin I to hypertensin II is crucial for its pressor activity in intact animals. The authors developed a method to purify the converting enzyme from horse plasma using ammonium sulfate fractionation and isoelectric precipitation. They also described a technique to estimate the enzyme's activity and demonstrated its effectiveness in converting purified hypertensin I to hypertensin II. The enzyme was found to be stable at pH 6.5 and active in the presence of sodium phosphate buffer. The study highlights the importance of the converting enzyme in the renin-hypertensin system and suggests that it may be a metalloprotein.The article by Skeeggs, Kahn, and Shumway explores the preparation and function of the hypertensin-converting enzyme. They discovered that hypertensin exists in two forms: hypertensin I, produced by renin, and hypertensin II, which is activated by an enzyme in the plasma requiring chloride ions. Both forms are pressor agents when injected intravenously, but hypertensin II is a potent vasoconstrictor, while hypertensin I is not. The conversion of hypertensin I to hypertensin II is crucial for its pressor activity in intact animals. The authors developed a method to purify the converting enzyme from horse plasma using ammonium sulfate fractionation and isoelectric precipitation. They also described a technique to estimate the enzyme's activity and demonstrated its effectiveness in converting purified hypertensin I to hypertensin II. The enzyme was found to be stable at pH 6.5 and active in the presence of sodium phosphate buffer. The study highlights the importance of the converting enzyme in the renin-hypertensin system and suggests that it may be a metalloprotein.