From colloids to proteases.

The present autobiographical review describes my professional experiences as a graduate student in Vienna, Austria, the postdoctoral experiences at the University of London, University of Minnesota, and at Cornell University, Ithaca, NY. This was followed by a faculty appointment at Duke University where I rose through the ranks from assistant professor to professor of physical biochemistry from 1938 to 1950. This account includes both scientific and cultural episodes and anecdotes. In 1950 I moved to Seattle to become founding chairman and professor in the Department of Biochemistry as will be described elsewhere.

Aspartic proteinases in fishes and aquatic invertebrates.

1. The literature on molecular properties and physiological role of aspartic proteinases in fishes and aquatic invertebrates has been reviewed. 2. Pepsins have not been detected in invertebrates, and apparently cathepsin D, as well as other cathepsins, act both as digestive and lysosomal enzymes in many of these animals. The molecular properties of invertebrate cathepsin D correspond with cathepsin D in fishes and mammalians. 3. Fishes with a true stomach have pepsinogen secretion. Fish pepsins have higher pH optimum and are less stable in strong acid conditions than mammalian pepsins. They are very efficient at low temperatures, but less thermostable than mammalian pepsins. 4. Many fishes have two significantly different pepsins: Pepsin I and Pepsin II, which digest haemoglobin at a maximal rate in the pH ranges 3-4 and 2-3 respectively. Usually the pI of Pepsin I is in the range 6.5-7, whereas pI of Pepsin II is about 4. 5. Fish Pepsin I and cathepsin D have very similar molecular properties, and a hypothesis proposing that cathepsin D is the ancestor enzyme of aspartic proteinases in higher animals is presented.