María Cecilia Arribére

Comparison of Asclepiadaceae latex proteases and characterization ofMorrenia brachystephana Griseb. cysteine peptidases

Partial characterization of the crude proteolytic extracts of five Asclepiadaceae species namely Araujia hortorum Fourn., Asclepias curassavica L., Funastrum clausum (Jacq.) Schlechter, Morrenia brachystephana Griseb. and Morrenia odorata (Hook. et Arn.) Lindley, and a comparison of these results and those from other Asclepiadaceae species are reported. Additionally, the crude extract from M. brachystephana was submitted to further purification and characterization. The crude enzyme showed high proteolytic activity when assayed on casein in the presence of 12 mM cysteine but was strongly inhibited by very low concentrations of sodium iodoacetate (0.01 mM) and mercuric chloride (0.1 mM) suggesting that the enzyme belongs to the cysteinyl-proteases type. Fractioned acetone precipitation followed by cation exchange chromatography allowed the separation of two basic ( pI > 9.3) proteolytically active fractions, both homogeneous by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and with similar molecular masses (25.5 and 26 kDa).Copyright

Comparison of two cysteine endopeptidases from latices of Morrenia brachystephana Griseb. and Morrenia odorata (Hook et Arn.) Lindley (Asclepiadaceae).

Abstract The properties of morrenain b II, a proteinase isolated from the latex of Morrenia brachystephana, were compared with those of morrenain o II, a proteinase obtained from the latex of Morrenia odorata. Both peptidases were purified to homogeneity by acetone precipitation followed by cation exchange chromatography. The enzymes have pI values higher than 9.3 and similar molecular masses (close to 26 kDa) as determined by SDSPAGE. They display maximum proteolytic activity within an alkaline pH range, and also exhibit esterolytic activity. The Nterminal sequences of morrenain o II and morrenain b II show a high degree of homology between each other and to other cysteine plant proteinases.

Morrenain b I, a Papain-Like Endopeptidase from the Latex of Morrenia brachystephana Griseb. (Asclepiadaceae)

A new cysteine endopeptidase (morrenain b I) has been purified and characterized from the latex of stems and petiols of Morrenia brachystephana Griseb. (Asclepiadaceae). Morrenain b I was the minor proteolytic component in the latex but showed higher specific activity than morrenain b II, which was the main active fraction. Both enzymes showed similar pH profiles and molecular masses, but kinetic parameters and N-terminal sequences were quite distinct, demonstrating that they are different enzymes instead of different forms of the same enzyme.