Crystalline Enzymes

Abstract

T?? chemical nature of enzymes has in the past been the subject of acute controversy. It has seemed impossible to many investigators to associate with molecules of. high molecular weight their extraordinary power of controlling the complex reaction of living systems. Yet it is becoming more and more difficult to separate the study of enzyme activity from that of the proteins with which it is associated, and this is particularly true when we deal with crystalline enzymes. The characteristic activity of enzymes provides the most delicate test for their presence; they may be detected in solutions much too dilute to give positive protein reactions. But the enzyme crystals so far obtained are all protein crystals, and their preparation has proved an important step in relating the chemistry of enzymes to that of proteins as a whole. Since Sumner's first isolation of crystalline urease in 1926, some twelve different enzymes have been obtained in crystalline forms the variety of which reflects their diverse and specific chemical character. Of these, one of the most remarkable groups is that of the proteolytic enzymes studied by Northrop and his collaborators. Northrop's present monograph is essentially an authoritative account of his own researches and does not deal, except in a general introductory way, with crystalline enzymes as such. It does include a general account of the problem of enzyme catalysis and reaction kinetics, but the sub-title of the book provides a more accurate description of its scope. For the principal beauty of Northrop's work lies not so much in the investigation of a large number cf different enzymes as in the isolation of several closely related proteins and the study of their reactions one with another. We have here the beginnings of a chemistry of pepsin and trypsin in the same sense that we might speak of the chemistry of aniline-including the preparation of crystalline derivatives and the conversion of one protein into another and related and crystalline protein. But this chemistry of molecules of weight 30,000-40,000 is on a different scale of magnitude altogether from that we are accustomed to meet in classical organic chemistry.

Crystalline Enzymes

The Chemistry of Pepsin, Trypsin and Bacterio-phage. (Columbia Biological Series, No. 12.) By John H. Northrop. Pp. xv + 176. (New York: Columbia University Press; London: Oxford University Press, 1939.) 15s. net.