Abstract
A protease called Mauritanicain was isolated from the latex of Euphorbia mauritanica L. (Euphorbiaceae) by combining ion exchange chromatography, ultrafiltration, and
gel filtration chromatography. It has a high proteolytic activity against casein.
The activity was only inhibited by specific serine protease inhibitors, classifying
it to the serine protease family. An optimal degradation of the substrate casein takes
place at a temperature of 55–65 °C and a pH of 5.5–6.5, and is unstable at pH < 5
and pH > 9. The protease is stable at temperatures from 20–70 °C, whereby the activity
decreases drastically to less than 20 % at 75 °C. SDS-PAGE and matrix-assisted laser
desorption time-of-flight analysis yielded a molecular weight of 73 kDa; possibly,
it is natively present as a non-covalently linked dimer of a higher molecular mass
> 132 kDa. Without heat denaturation, a breakdown in fractions of 73 kDa and 52 kDa
was observed in SDS-PAGE. Only in some properties it shows a similarity to other characterized
proteases in the plant family Euphorbiaceae, such that Mauritanicain can be presented
as a new isolated protease.
Key words
Euphorbia mauritanica
- Euphorbiaceae - Mauritanicain - serine protease - plant protease - latex
