The gastric aspartic proteinases (pepsin A, pepsin B, gastricsin and chymosin) are synthesized in the gastric mucosa as inactive precursors, known as zymogens. The gastric zymogens each contain a prosegment (i.e. additional residues at the N-terminus of the active enzyme) that serves to stabilize the inactive form and prevent entry of the substrate to the active site. Upon ingestion of food, ea...

A detailed understanding of gene structure and expression in lactic acid bacteria is essential for the successful application of genetic modification techniques for both the improvement of these bacteria used in industrial dairy and food fermentations and their use as food-grade production organisms. This paper is intended to review the organization and expression of homologous and heterologous...

Bovine chymosin is an important milk-clotting agent used in the manufacturing of cheeses. Currently, the production of recombinant proteins by genetically modified organisms is widespread, leading to greatly reduced costs. Lactococcus (L.) lactis, the model lactic acid bacterium, was considered a good candidate for heterologous chymosin production for the following reasons: (1) it is considered...

Confluent monolayers of MDCK (Madin-Darby canine kidney) cells provide a widely used system to study the biogenesis of epithelial cell polarity. We now report that these cells are also capable of the vectorial constitutive secretion of a major endogenous product, a glycoprotein of 81 kDa, which is released into the medium from the apical surface within 30 min of its synthesis. This release repr...

Gastric aspartic proteases (AP) are among proteolytic enzymes that are widely distributed in vertebrates. They are responsible for the digestion of dietary proteins and are synthesized as inactive precursors (prochymosin, pepsinogen and progastricsin), commonly known as zymogens. One part of their secretion by mucous neck and chief cells in the gastric mucosa (2, 22, 23) reaches the blood strea...

Two pepsinogens (pepsinogens 1 and 2) were purified from the esophageal mucosa of the bullfrog (Rana catesbeiana), and their molecular weights were determined to be 40,100 and 39,200, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The NH2-terminal 70-residue sequences of both pepsinogens are the same, including the 36-residue activation segment. Furthermore, a cDNA ...

Bovine pepsinogen is converted into pepsin by removal of 45 amino acid residues from the NH, terminus of the single polypeptide chain. The complete sequence of the activation peptides has been deduced from two overlapping sets of peptides, one set obtained by autoactivation of the zymogen at pH 2 and the second set from a tryptic digest of maleylated pepsinogen. A peptide derived from the 17 re...

components, chymosins I and 11, by column chromatography on DEAE-cellulose (Fig. 1). The same characteristic profile was obtained from four different animals. Pooled fractions of chymosins I and I1 were examined by urea/polyacrylamide-gel electrophoresis, and each consisted of one major protein species, with chymosin I1 showing a slightly higher electrophoretic mobility than chymosin I. Chymosi...