Crystalline Enzymes

In this monograph, Northrop summarizes the work on proteolytic enzymes and on the bacteriophage which has been carried out in his laboratory at the Rockefeller Institute for Medical Research in Princeton during the past ten years. After a brief introduction, dealing with the fundamentals of enzymatic catalysis, the preparation in crystalline or purified form and the properties of the following substances are described: pepsin, pepsinogen, chymo-trypsin, chymo-trypsinogen, trypsin, trypsinogen, trypsin-inhibitor, and staphylococcus phage. Not only is the text lavishly illustrated by photomicrographs of exquisitely formed enzyme crystals and by many graphs, but a large number of tables and an appendix dealing with experimental procedures supply the reader with detailed information on the preparation and the assay for catalytic activity of the various materials. This makes it almost unnecessary to consult the original publications from the author's laboratory. As a matter of fact, the student of enzyme chemistry will find the small book just as valuable as a laboratory manual as it is a satisfying authoritative report on work which is already recognized as classic, both in the fields of enzymes and of protein chemistry in general. A more critically inclined reviewer might take exception to the title of the monograph. The heading "Crystalline Enzymes" conflicts with the subheading "The Chemistry of Pepsin, Trypsin, and Bacteriophage," because the latter substance has neither been obtained in crystalline state nor has its enzymatic nature been established. Moreover, it becomes more and more doubtful whether the fact that a given protein, be it an enzyme or a hormone, has been prepared in crystalline state still deserves the emphasis which has been accorded to it in the past decade. Crystallinity as a criterion of purity or homogeneity has lost much of its weight for the special case of proteins. To quote from Northrop and Kunitz's recent contribution to the S6rensen volume of the Comptes rendues du Laboratoire de Carlsberg (1937):