Metabolic Regulation of Polygalacturonic Acid trans‐Eliminase in Erwinia

Strains of Erwinia carotovora and Erwinia aroideae , formerly thought only to be inducible, are constitutive for polygalacturonic acid trans ‐eliminase. Maximum enzyme formation, however, occurs in the presence of polygalacturonic acid. A release from strong catabolic repression enables glucose‐grown cultures to initiate their attack on polygalacturonic acid and, thereby, eliminates the necessity for the entry of the polymer into the cell. A low constant proportion (less than 25%) of the total polygalacturonic acid trans ‐eliminase is present in the culture fluid during the exponential growth‐phase of Erwinia carotovora . The enzyme may be regarded as an exoenzyme. The exact location of polygalacturonic acid trans ‐eliminase in the cells was not established; it could be truly intracellular or reside between the cell‐wall and membrane.