Physicochemical Properties of the Proteolytic Enzyme From the Latex of the Milkweed, Asclepias Speciosa Torr. Some Comparisons With Other Proteases

Abstract

1. A study has been made of the properties of a hitherto unreported proteolytic enzyme from the latex of the milkweed, Asclepias speciosa. The new protease has been named asclepain by the authors. 2. The results of chemical, diffusion, and denaturation tests indicate that asclepain is a protein. 3. Like papain, asclepain dots milk and digests most proteins, particularly if they are dissolved in concentrated urea solution. Unlike papain, asclepain did not clot blood. 4. The activation and inhibition phenomena of asclepain resemble those of papain, and seem best explained on the assumption that free sulfhydryl in the enzyme is necessary for proteolytic activity. The sulfhydryl of asclepain appears more labile than that of papain. 5. The measurement of pH-activity curves of asclepain on casein, ovalbumin, hemoglobin, edestin, and ovovitellin showed no definite digestion maxima for most of the undenatured proteins, while in urea solution there were well defined maxima near pH 7.0. Native hemoglobin and ovovitellin were especially undigestible, while native casein was rapidly attacked. 6. Temperature-activity curves were determined for asclepain on hemoglobin, casein, and milk solutions. The optimum temperature was shown to increase with decreasing time of digestion.

Stability, purification, and applications of bromelain: A review

“…Winnick, Davis and Greenberg observed that the rate of bromelain inactivation follows a first order reaction at 55 and 60°C; however, at temperatures above 70°C, the destruction of enzyme is not a first order reaction. The process of bromelain thermal denaturation studied by circular dichroism (CD), and differential scanning calorimetry (DSC) is completely irreversible and apparently follows a simple two‐stage mechanism, where an intermediate exists between the native and denatured states …”

Occurrence and Properties of Proteases in Plant Latices

“…Both are members of Asclepiadaceae family. There are both inhibited by cysteine-specific inhibitors (e. g., iodoacetic-acid) [55]. Calotrop(a)ins DI, DII, FI, FII: There are at least four cysteine proteases purified from the latex of Calotropis gigantea (L.) Dryand.…”

Funastrain c II: A Cysteine Endopeptidase Purified from the Latex of Funastrum clausum

“…The latex of the Asclepiadaceae plant family usually contains proteases. Studies were made on few genera such as Asclepias (Barragán et al, 1985;Brockbank and Lynn, 1979;Carpenter and Lovelace, 1943;Greenberg and Winnick, 1940;Lynn et al, 1980;Tablero et al, 1991;Winnick et al, 1940) and Calotropis Joshi, 1979a, 1979b;Pal and Sinha, 1980;Sengupta et al, 1984). Recently, some cysteine proteases from plants belonging to this family were purified and characterized in our laboratory from the latex of Morrenia brachystephana and Morrenia odorata (Arribére et al, 1998;Vairo Cavalli et al, 2001, Araujia hortorum (Obregón et al, 2001;Priolo et al, 2000), and Asclepias fruticosa (Trejo et al, 2001).…”