Bacillus subtilis α-amylase:: the rate limiting step of secretion is growth phase-independent

When Bacillus subtilis alpha-amylase was expressed under the control of sacR in a degU32(Hy) strain, the production of exoenzyme occurred during both the exponential and stationary phases of growth. In each phase, pulse-chase experiments showed that the rate-limiting step of the secretion process was the release of the processed form of the protein in each physiological context. The rate of this event was slightly slower (t(1/2)=3.2 min) during the stationary phase than during the exponential phase (t(1/2)=2 min). The effecters which possibly control the efficiency of the release stage, the level of PrsA or the calcium binding properties of the cell wall, remained unchanged throughout growth phases. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.