Studies of an anionic trypsinogen and its active enzyme from porcine pancreas
Journal of Biological Chemistry
An anionic trypsinogen has been identified and isolated in a state of high purity from porcine pancreatic tissue and juice extracts. The anionic trypsinogen is present in large amounts and accounts for about half of the total potential tryptic activity. The kinetics of the conversion of the anionic trypsinogen to active enzyme is autocatalytic, yielding an anionic trypsin which is less anionic than the zymogen. K, values and specific activities of anionic trypsin toward esters and anilides of
... s and anilides of arginine and lysine were found to be very similar to those of cationic trypsin. Soybean trypsin inhibitor and diisopropyl phosphorofluoridate are potent inhibitors of anionic trypsin. A previous publication (1) from this laboratory showed that extracts of acetone powders from porcine pancreas contained large amounts of a hitherto unreported endopeptidase having substrate specificities similar to trypsin. The endopeptidase and its zymogen precursor have a low isoelectric point as indicated by their elution from a DEAE-cellulose column with a decreasing pH gradient and by their electrophoretic properties on starch and acrylamide gels. The enzyme was tentatively called protease A. Further investigations of protease A, based upon the hydrolysis of several synthetic trypsin substrates as well as proteins, have amply confirmed its trypsin-like nature. Because of their anionic behavior and the trypsin-like properties of the active enzyme, protease A and its zymogen are called anionic trypsin and anionic trypsinogen, respectively. The anionic nature of this new enzyme is in marked contrast to the trypsins which have been isolated from porcine pancreas by several investigators in the past decade. Buck et al. (2), as well as Travis and Liener (3), have by free boundary electrophoresis determined the isoelectric point of porcine cationic trypsin to be 10.3 and 10.7, respectively. Charles et al. (4) have reported that porcine trypsinogen has an isoionic point of 7.5. The behavior of the isolated porcine trypsinogen and trypsin, on carboxymethyl cellulose, as reported by the above investigators is in accord with the basic or cationic properties of the zymogen and active enzyme.