Captopril Inhibits Peptidylglycine- α-Hydroxylating Monooxygenase: Implications for Therapeutic Effects

Abstract

The therapeutic actions of captopril are facilitated by its sulfhydryl moiety which interacts with the metal (Zn²⁺) prosthetic groups of angiotensin-converting enzyme (ACE; EC 3.4.15.1). This study focused on captopril as an inhibitor of another metal-dependent (Cu²⁺) enzyme, peptidylglycine-α-hydroxylating monooxygenase (PHM; EC 1.14.17.3). PHM is rate limiting in α-amidation, a COOH-terminal modification that bioactivates several pressor peptides. Captopril inhibited PHM in vitro in a dose-dependent manner with an IC₅₀ of approximately 100 μmol/l. This inhibition was partially reversed by increased concentrations of Cu²⁺. Structurally similar nonsulfhydryl ACE inhibitors did not affect the activity of PHM. The present findings indicate that the therapeutic effectiveness of captopril may result from actions on a range of metalloenzymes including ACE and PHM.

Thiorphan, tiopronin, and related analogs as substrates and inhibitors of peptidylglycine α‐amidating monooxygenase (PAM)

“…Sulfur-containing ligands bind strongly to Cu(II). Possible explanations for the results presented here, and other reports on the inhibition of PAM and DbM by sulfur-containing ligands [37][38][39][40], is that the sulfur-containing ligands either chelate to active site copper, forming an E-2Cu(II) AE inhibitor complex, or remove the active site copper, forming a copper-free-E and separate Cu(II) AE inhibitor complexes. The copper-free forms of PAM and DbM are inactive [41,42].…”

“…PAM and the related enzyme, dopamine β‐monooxygenase (DβM), are both copper‐dependent monooxygenases with 2 bound copper atoms per active site [26,34–36]. The inhibition of PAM by homocysteine‐extended peptides [37] and by captopril ((2 S )‐1‐(3‐mercapto‐2‐methylpropionyl)‐ l ‐proline) [38] has been attributed to the interaction of a sulfur atom with enzyme‐bound copper. Similarly, inhibition of DβM by captopril, cysteine, and glutathione has been ascribed to in situ chelation of the enzyme‐bound coppers [39,40].…”

Peptidylglycine-α-Hydroxylating Monooxygenase Generates Two Hydroxylated Products from Its Mechanism-Based Suicide Substrate, 4-Phenyl-3-butenoic Acid

“…Recrystallization from water raised the mp to 89-92 °C; negative ion electrospray showed an (M-H)ion at m/z 177. 1 (32) and purified as described previously (33). PHM protein recovered from 1 L of culture medium was 2.25 mg at a purity of >98% as assessed by silver-stained SDS-polyacrylamide gel electrophoresis.…”

Angiogenesis and Cancer Control: From Concept to Therapeutic Trial

“…132, 133 Used commonly as an inhibitor of the angiotensin converting enzyme to treat hypertension, the sulfhydryl group enables captopril, like penicillamine, to convert plasminogen to angiostatin. 70 Captopril is known to be a chelator of copper, 134,135 or to function as a metalloprotease inhibitor. 136 There is anecdotal evidence that captopril, combined with urokinase, causes regression of an advanced refractory malignancy.…”