Crystalline fumarase is rapidly inactivated by incubation with bacterial proteinase at pH 7.4. The amino acids and peptides liberated during digestion of the enzyme protein by proteinase were measured using the dinitro-fluorobenzene method. Evidence is given that the inactivation is caused by proteolytic action of the proteinase. Comparison of the dinitrofluorobenzene and Folin-Ciocalteu methods are also reported.
