A bacterial extracellular proteinase degrading silk fibroin

The bacterium Variovorax as paradoxus, grown in a minimal medium in which s ilk fibroin represents the sole source of carbon and nitrogen, produces an extracellular protease that hydrolyzes fibroin as well as casein and, to a smaller extent, collagen and albumin. The optimal pll For activity was foun d to be in the acid range (optimum pH 5.8-6.4) and the enzyme activity was stimulated by the addition of divalent cations, either manganese or magnesi um. Gel permeation chromatography and SDS-PAGE provided evidence that the n ative enzyme is a monomer with a M-r of ca. 21 kDa. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.