MACRODONTIN, A NEW PROTEASE ISOLATED FROM FRUITS OF PSEUDANANAS MACRODONTES (MORR) HARMS (BROMELIACEAE)

A cysteine proteinase was isolated from immature fruits of Pseudananas macrodontes (Morr.) Harms, a species taxonomically close to pineapple grown in the northeast of Argentina. The protease is active at pH 7.0 to 10.5, and rather unstable at temperatures over 45C. Crude extracts were purified by acetone fractionation followed by chromatofocusing a t the pH range 4.5 to 6.5. Two main proteolytic fractions were obtaine d: fraction I (M(r) = 20.6 kDa, pI = 5.9) and fraction II (M(r) = 19.3 kDa, pI = 5.3), both homogeneous by gel-filtration and SDS-PAGE crite ria. This new plant protease (''marcrodontin'') could be valuable in p rocesses carried out in neutral-weak alkaline media. The thermal behav ior of the crude enzyme is also a useful property, since it could be e asily inactivated in foodstuffs by heating 10 min at 75C. Comparison o f macrodontin and alcalase proteolytic behavior on soy concentrates is presented.