Studies on the Interaction between Regulatory Enzymes and Effectors

Biodegradative l-threonine deaminase from Escherichia coli was isolated and crystallized in the presence of AMP. The enzyme was homogeneous as judged by ultracentrifugation and starch gel electrophoresis. The molecular weight was estimated to be approximately 147,000, and the amino acid composition was determined. The enzyme had a marked yellow color with an absorption maximum at 415 mµ and contained 4 moles of pyridoxal phosphate per mole of protein. It was found that the crystalline enzyme binds 4 moles of AMP per mole of enzyme.