Mandelstam investigated the induced synthesis of lysine decarboxylase in Bacterium cadaveris using washed cell suspensions. The enzyme is produced only when glucose and lysine are present together. Under anaerobic conditions, the rate of enzyme synthesis is directly proportional to substrate saturation, correlating with the enzyme's Michaelis constant. However, under aerobic conditions, enzyme synthesis proceeds at a maximal rate even when substrate concentration is very low and saturation is minimal. The pH optimum for enzyme synthesis closely matches that for enzyme activity. Lysine analogues fail to induce synthesis. Adapted cells undergo de-adaptation when incubated with glucose alone, a phenomenon caused by cadaverine (the decarboxylation product) affecting the pyridoxal phosphate cofactor rather than degrading the apoenzyme itself. These findings provide evidence for distinguishing between competing theories of enzyme induction—the 'mass action' theory versus the 'catalyst' theory—though neither fully explains all observations without additional assumptions.

Key findings

• Lysine decarboxylase synthesis requires simultaneous presence of glucose and lysine substrate; D-lysine and lysine analogues are inactive as inducers
• Anaerobic enzyme synthesis rate correlates directly with degree of enzyme saturation by substrate, while aerobic synthesis proceeds at maximal rate even at very low substrate concentrations
• pH optimum for enzyme synthesis closely parallels pH optimum for enzyme activity, both peaking at pH 5.3-5.6
• De-adaptation of adapted cells occurs through cadaverine-induced loss of pyridoxal phosphate cofactor, not apoenzyme degradation
• Results are more consistent with a 'catalyst' mechanism of enzyme induction than 'mass action' theory, though aerobic and anaerobic conditions show divergent kinetics