New observations on proteases of the human hookworm Necator americanus.

Two protease populations have been identified in the somatic products of adult Necator americanus. One population (158, 138, 34 and 31 kDa) loses, whereas the other population (107, 74, 51 and 20 kDa) retains, its proteolytic activity after elution from substrate gels. The present study warns that hookworm proteases may oligomerise and/or lose their activity under the conditions necessary for their purification. We suggest that following assessment of protease activity on substrate gels, the protease of interest should be eluted from plain gels; their isolation from substrate gels may lead to a reduced or no yield.