Northrop's Phenomenon

Abstract

Northrop (6,8) observed that the digestion of casein and gelatin by crude and crystalline trypsin proceeded at the same rate whether present in separate solutions or in the same solution. Northrop (10) pointed out that this fact could not be explained if it is supposed that an intermediate enzyme-substrate compound is formed according to addition compound theory, unless it be assumed either that there are two enzymes or two different active groups, which amounts to practically the same thing.As a first point under consideration, the question arises whether this phenomenon is specific for trypsin-casein or whether it is general for all proteases and for other substrates different from casein. In this work, the behavior of crude and crystalline trypsin, papain, and pepsin with respect to casein and hemoglobin either alone or in the presence of gelatin was studied in an attempt to give, partially at least, an answer to this question. EXPERIMENTALEnzymes. Trypsin, twice crystallized salt-free, and crude pancreatic protease, Worthington. Papain, twice crystallized, lyophilized, and lyopMl~.ed fraction 3A, Worthington. Pepsin, Worthington twice crystallized, and Dffco crude pepsin.S o l~.