Enalaprilat is a competitive inhibitor of the angiotensin-converting enzyme (ACE), which cleaves the blood-pressure regulating peptide angiotensin  I. ACE has a KM = 52 ?M for angiotensin  I, which is present in plasma at a concentration of 75 ?M. When enalaprilat is present at 2.4 nM, the activity of ACE in plasma is 10% of its uninhibited activity. What is the value of KI for enalaprilat?