John Howard Northrop

John Howard Northrop (1891–1987) was an American biochemist who crystallized digestive enzymes and viruses. He shared the 1946 Nobel Prize in Chemistry for preparing enzymes in pure form.

James Batcheller Sumner: An American chemist who first crystallized an enzyme, urease, and shared the 1946 Nobel Prize in Chemistry. Sumner’s enzyme crystallization preceded Northrop’s and helped establish the field they both advanced.
Protein crystallization: The formation of ordered protein crystals from a solution under controlled conditions. Northrop used crystallization to isolate enzymes in forms that could be studied as chemical substances.
Vitalism: The doctrine that living processes depend on a special principle absent from nonliving matter. Northrop’s isolable enzyme crystals supported chemical explanations of biological catalysis rather than vital forces.
Enzyme purification: The separation of an enzyme from other substances while retaining measurable catalytic activity. Northrop’s repeated crystallizations became a model for obtaining enzymes in highly purified form.
Wendell Meredith Stanley: An American biochemist who crystallized tobacco mosaic virus and shared the 1946 Nobel Prize in Chemistry. Stanley’s virus crystallization formed the third part of the Nobel-recognized work alongside Northrop’s enzyme studies.
Pepsin: A stomach enzyme that breaks proteins into smaller peptides in acidic conditions. Northrop crystallized pepsin, providing a purified enzyme preparation for chemical analysis.
Enzyme theory: The account of enzymes as specific biological catalysts that act on particular chemical reactions. Northrop’s experiments supplied purified materials for testing what enzymes are and how they act.
Protein chemistry: The study of the chemical composition, structure, and reactions of proteins. His work helped make enzymes accessible to direct chemical characterization.
Moses Kunitz: An American biochemist known for protein purification and enzyme research at the Rockefeller Institute. Kunitz collaborated with Northrop on the purification and crystallization of digestive enzymes.
Trypsin: A digestive enzyme that cleaves proteins, produced as the inactive precursor trypsinogen. Northrop crystallized trypsin and investigated its relationship to trypsinogen.

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James B. SumnerRelated: His independent enzyme crystallizations reinforced Sumner’s claim that enzymes are proteins.