Extracellular Enzymes

Industrial enzymes that are almost invariably extracellular proteins, in that they are prepared from the fermentation broth rather than from the cells, are considered. In the case of bacterial enzymes, the producer-organisms are Gram-positive with the sole exception of Klebsiella aerogenes (K. pneumoniae). The mechanism of secretion is considered and current models of the transport of proteins across membranes are outlined. Regulation of extracellular enzyme synthesis is then discussed. During the past decade, protein secretion in bacteria has been intensively studied and our knowledge of the process in E. coli now outstrips our understanding of eukaryotic systems. It would seem that the translocation of the protein across the membrane and the role of signal (leader) peptides in the process is essentially the same in both types of cell although the details may vary. Virtually nothing is known about the molecular mechanisms of the regulation of extracellular enzyme synthesis in bacteria and fungi.