Regulation of extracellular protease formation by Serratia marcescens

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Abstract
Heavy cell suspensions of S. marcescens, when grown in gelatin-containing media, produce extracellular proteases which increase in specific activity in a linear fashion for 3-4 h. During partial purification, a single peak of proteolytic activity was demonstrated by Sephadex G-100 chromatography. Electrophoresis using 5% polyacrylamide gels discloses 3 proteolytically active bands. Evidence in favor of gelatin acting as an inducer of the proteolytic system was provided by 2 observations. First, proteolytic activity is only present in media containing gelatin. Secondly, the addition of 10-4 M rifampicin to cells growing in gelatin-containing medium plus an additional C source inhibits protease activity totally, but has no effect on growth. When glycerol is added to a growing cell suspension in gelatin-containing medium, growth increases, but protease specific activity decreases. This glycerol effect is not due to an accumulation of active or inactive enzyme in association with the cell, nor to a decrease in the total number of proteases synthesized. Rather, glycerol, as other utilizable carbohydrates, exerts a repression which can be eliminated by 5 mM dibutyryl cyclic AMP.

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