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

When Bacillus subtilis alpha-amylase was expressed under the control of sac R 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 wa s the release of the processed form of the protein in each physiological co ntext. The rate of this event was slightly slower (t(1/2)=3.2 min) during t he stationary phase than during the exponential phase (t(1/2)=2 min). The e ffecters which possibly control the efficiency of the release stage, the le vel of PrsA or the calcium binding properties of the cell wall, remained un changed throughout growth phases. (C) 1999 Federation of European Microbiol ogical Societies. Published by Elsevier Science B.V. All rights reserved.