Isolation and characterization of an Aspartic Protease from Salpichroa origanifolia Fruits.

ROCHA GABRIELA; OBREGÓN, WALTER D.; MUÑOZ FERNANDO; GUEVARA MARÍA GABRIELA

PROTEIN AND PEPTIDE LETTERS

BENTHAM SCIENCE PUBL LTD

Año: 2015

0929-8665

This report describes the purification of an aspartic protease (salpichroin) from ripe fruits of Salpichroa origanifolia (Solanaceae) starting with precipitation using organic solvents and anion-exchange chromatography with 32.1% recovery and 13.4-fold purification. SDS-PAGE and zymograms of this enzyme showed a single band corresponding to an apparent molecular mass of approximately 32 kDa. The biochemical and kinetic characterization of the pure enzyme showed an acidic behavior with an optimal pH value around 3.0-4.5 with hemoglobin and 5.5-6.0 with casein. Salpichroin activity was inhibited by pepstatin but not by phenylmethylsulfonyl fluoride, E-64, EDTA or 1,10-phenanthroline, thus suggesting an aspartic protease behavior. Salpichroin hydrolyzed natural substrates, such as casein and hemoglobin, with high specific activity. Kinetic studies conducted with the synthetic peptide H-Pro-Thr-Glu-Phe-p-(NO2)-Phe-Arg-Leu-OH showed lower affinity (Km 494 µM) than other representative aspartic proteases. By investigating the cleavage of oxidized insulin β-chain to establish the hydrolytic specificity of salpichroin, we found six cleavage sites on the substrate of peptide bonds similar to those of chymosin. MALDI-TOF(/TOF)-MS of the tryptic in-gel digest of salpichroin showed that the isolated protease shared homologous sequences with other plant proteases of the A1 aspartic protease family. This is the first report concerning the isolation and biochemical characterization of an aspartic protease isolated from Salpichroa origanifolia fruits