The properties of L-aspartate α-decarboxylase [EC 4. 1. 1. 11] in a crude extract and in a partially purified preparation from E. coli B were studied.
1. Adaptation of the bacteria to substrate by growth in synthetic medium containing 1.5% L-aspartic acid and 0.5% L-glutamic acid before culture in the same medium greatly increased enzyme production. Enzymatic activity increased with bacterial growth to a maximum in the later stage of the logarithmic phase and decreased promptly toward the beginning of the stationary phase, indicating that the enzyme was formed to supply β-alanine required during bacterial growth for biosynthesis of pantothenic acid. Formation of β-alanine from uracil by adapted bacteria was rather slight.
2. The optimum pH of this enzyme was 5.5 and the optimum temperature was rather broad, being 37-47°C. With a partially purified enzyme preparation the Michaelis constant was calculated to be 1, 5×10^-3M.
3. Pyridoxal 5'-phosphate, α-keto acids and Co²⁺ and Mg²⁺ ions activated the enzyme, and their effects were additive. A combination of pyridoxal 5'-phosphate, α-keto-glutaric acid and Co²⁺ enhanced the enzymatic activity about 13-fold. Cyanide, fluoride, Ag⁺, Hg²⁺, semicarhazide, thiourea and isonicotinic acid hydrazide inhibited the decarboxylase.