Antioxidant Peptides with Angiotensin Converting Enzyme Inhibitory Activities and Applications for Angiotensin Converting Enzyme Purification

Abstract

Five commercial peptides, namely, reduced glutathione (GSH), oxidized glutathione (GSSG), carnosine, homocarnosine, and anserine, were used to test angiotensin converting enzyme inhibitory (ACEI) activities using N-[3-(2-furyl)acryloyl]-Phe-Gly-Gly (FAPGG) as a substrate. All of these peptides showed dose-dependent ACEI activities. Using 50% inhibition (IC(50)) of captopril as 0.00781 microM for the reference, the IC(50) values of GSH, carnosine, homocarnosine, and anserine were determined to be 32.4 microM, 5.216 mM, 6.147 mM, and 6.967 mM, respectively. GSH or carnosine showed mixed noncompetitive inhibition against ACE. When 0.0164 mM GSH or 0.4098 mM carnosine was added, the apparent inhibition constant (K(i)) was 49.7 microM or 3.899 mM, respectively. Commercial glutathione-Sepharose 4 fast flow, GSH-coupled CNBr-activated and GSH-coupled EAH-activated Sepharose gels were used for ACE purification. Commercial ACE could be adsorbed only by EAH-coupled GSH gels and eluted off the gels by increasing salt concentrations. These EAH-coupled GSH gels might be developed as affinity aids for ACE purification.

Interactions between Carnosine and Captopril on Free Radical Scavenging Activity and Angiotensin-converting Enzyme Activity in vitro

“…3B). The present results are comparable with those of Hou et al 9) on the point that the inhibition was not in a competitive manner. In addition, no synergistic eŠects on ACE activity were found in the presence of carnosine and captopril (Fig.…”

“…Assay for ACE Activity The ACE activity was spectrophotometrically measured according to the method of Hou et al 9) with a slight modiˆcation. Forty microliters of commercial ACE (0.5 units/ml, from bovine lung) were mixed with 200 ml of a sample solution, which was prepared with 50 mM Tris-HCl buŠer (pH 7.5) containing 0.3 M NaCl, and 200 ml of 50 mM Tris-HCl buŠer (pH 7.5) containing 0.3 M NaCl in the cuvette of a spectrophotometer maintained at 30°C.…”

“…Additionally, carnosine has been documented to inhibit ACE activity. 9) On the other hand, captopril, which has a sulfhydryl (SH) group in its chemical structure, has a role as a free radical scavenger 10,11) in addition to its use as a prevailing ACE inhibitor to treat hypertension. In the present study, we examined interactions between carnosine and captopril on free radical scavenging activity and ACE activity in vitro.…”

Which Comes First—Renal Dysfunction or High Blood Pressure?

“…A conceptual framework, which would link hypertension to a predisposition of glomeruli to injury, has been proposed by Brenner. He postulated that a low number of nephrons predisposes not only to hypertension, but also to a greater susceptibility to renal injury (24). At least as far as the postulated lower nephron endowment in essential hypertension is concerned, this hypothesis has been confirmed (25).…”

“…It scavenges reactive oxygen species (23) and reacts with macromolecular carbonyls (22). It also inhibits ACE (24). These are all properties that would interfere with initiation and progression of diabetic nephropathy and conceivably also with other microand macrovasular complications of diabetes.…”