Purification Of Angiotensin I-converting Enzyme Research Articles

Immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether for purification of angiotensin I-converting enzyme inhibitory peptide from casein hydrolysate

Purification of small bioactive peptides from complex biological samples is a difficult task due to the interference of concentrated large biomolecules. In this study, a magnetic immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether (IMACM@mPEG) was prepared and applied for the rapid purification of angiotensin I-converting enzyme (ACE) inhibitory peptides from casein hydrolysate. The proposed IMACM@mPEG considerably reduced the non-specific adsorption of large proteins and exhibited improved purification efficiency towards ACE inhibitory peptides. A novel peptide with moderate ACE inhibitory activity (IC50 value of 274 ± 5 μM) was identified as LLYQEPVLGPVR. Lineweaver-Burk plot confirmed the non-competitive inhibition pattern of LLYQEPVLGPVR. The purified peptide was digested after simulated gastrointestinal digestion and produced shorter peptides which contributed to enhanced ACE inhibitory activity. These results indicated that the IMACM@mPEG is an effective method for the prepurification of ACE inhibitory peptide and the purified peptide LLYQEPVLGPVR may have potential as nutraceutical ingredient in functional foods for hypertension treatments.

Purification of angiotensin I-converting enzyme (ACE) inhibitory peptides from casein hydrolysate by IMAC-Ni2.

Casein proteins were hydrolyzed by papain to identify inhibitory peptides of angiotensin I-converting enzyme (ACE). The hydrolysate was fractionized by immobilized metal affinity chromatography (IMAC-Ni2+). The fraction with high ACE inhibitory activity was enriched and further chromatographed on a reverse-phase column to yield four fractions. Among the fractions, the L4 fraction exhibited the highest ACE inhibitory activity and was identified by sequence analysis as Trp-Tyr-Leu-His-Tyr-Ala (WYLHYA), with IC50 value of 16.22±0.83µM in vitro. This peptide was expected to be applied as an ingredient for preventing hypertension and IMAC-Ni2+ may provide a simple method for purification of ACE inhibitory peptides.

Purification of angiotensin I converting enzyme from pig lung using concanavalin-A sepharose chromatography

Angiotensin I converting enzyme (ACE) plays a major role in blood pressure regulation, catalyzing the conversion of angiotensin I to the vasoconstrictor angiotensin II. In this report we describe a two-step affinity chromatography method for preparative purification of ACE from pig lung using Concanavalin-A Sepharose 4B and affinity chromatography on Lisinopril Sepharose 6B. The same purification scheme was used to obtain Cobalt-ACE, where zinc ion located at the active site is replaced by cobalt. Cobalt-ACE visible spectrum shows a characteristic broad peak from 500 to 600 nm. The shape and maximum absorptivity of this peak changes in presence of ACE inhibitors that bind at the catalytic site.

Purification and analysis of lung and plasma angiotensin I-converting enzyme by high-performance liquid chromatography

We purified angiotensin I-converting enzyme (ACE) from pig and human lung and plasma for comparison of some physicochemical properties between the endothelial membrane-bound form and the soluble form of the enzyme. After affinity chromatography on Sepharose CL-4B/lisinopril, gel-filtration HPLC on Superose 12 achieved homogeneity for both forms as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Whatever the source of ACE, the molecular weight was 300 ± 40 kDa after calibration of Superose 12 with standard globular proteins and 172 ± 4 kDa by SDS-PAGE, with or without reduction, a result suggesting interactions between the glycopolypeptide chain and the chromatographic gel possibly related to the overall shape and sugar content of the enzyme. Ion-exchange HPLC analysis on TSK-DEAE showed that the membrane-bound and soluble forms of ACE are not isoenzymes, although isoelectrofocusing did show that the isoelectric point of soluble ACE was lower than those of tissue ACE, suggesting a different glycosylation. No significant difference between porcine and human ACE appeared. HPLC methods seem to be of particular interest for the purification of ACE with a high yield and for the analysis of its putative differently glycosylated isoforms.

Large-scale purification of angiotensin I-converting enzyme from human plasma utilizing an immunoadsorbent affinity gel

Angiotensin I-converting enzyme was purified 1500-fold from human plasma utilizing an immunoadsorbent affinity gel prepared by coupling antibody to baboon lung angiotensin I-converting enzyme to CNBr-activated Sepharose 4B. The enzyme was eluted from the gel using 2 m magnesium chloride, pH 5.8. Subsequent hydroxylapatite and Sephadex G-200 chromatography yielded 2.6 mg of homogenous enzyme with a specific activity of 40 units/mg with hippuryl- l-histidyl- l-leucine as substrate from 48 liters of plasma. Use of the immunoadsorbent allowed the 48 liters of plasma to be processed in one-half the time it previously took to process 2 liters of plasma by other methods. This protocol enables us to obtain sufficient amounts of enzyme for structural studies that were previously impossible because of insufficient amounts of enzyme.

Purification of angiotensin I-converting enzyme from human lung

Angiotensin I-converting enzyme (peptidyl dipeptide hydrolase, EC 3.4.15.1) was solubilized from the membrane fraction of human lung using trypsin treatment and purified using columns of DE 52-cellulose, hydroxyapatite and Sephadex G-200. The purified enzyme was shown to convert angiotensin I to angiotensin II and also to inactivate bradykinin. The specific activity of the enzyme was 9.5 units/mg protein for Hippuryl-His-Leu-OH and 0.665 μmol/min per mg protein for angiotensin I. The enzymic activity obtained after trypsin treatment (1 mg/200 mg protein) for 2 h could be divided into three components: (i) an enzyme of molecular weight 290 000 (peak I), (ii) an enzyme of molecular weight 180 000 (peak II) and (iii) an enzyme of molecular weight 98 000 (peak III), by columns of DE 52-cellulose and Sephadex G-200. K m values of peak I, II and III fraction for Hippuryl-His-Leu-OH were identical at 1.1 mM. pH optimum of the enzyme was 8.3 for Hippuryl-His-Leu-OH.

Affinity chromatography of angiotensin I-converting enzyme from rabbit lung using hippurylhistidylleucyl-OH

Approximately 50-fold purification of angiotensin I-converting enzyme (Peptidyldipeptide hydrolase, EC 3.4.15.1) from rabbit lung was achieved by affinity chromatography using the synthetic substrate Hippuryl-His-Leu-OH. The specific activity of the enzyme was increased from 0.044 units/mg protein to 1.911 units/mg protein for Hippuryl-His-Leu-OH and from 0.33 nmol/ min per mg protein to 13.8 nmol/min per mg protein for angiotensin I.