Purification and properties of a novel arylmalonate decarboxylase from Alcaligenes bronchisepticus KU 1201

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Abstract
A novel decarboxylase which catalyzes an enantioselective decarboxylation of α-aryl-α-methylmalonates to α-arylpropionates has been purified from a soil bacterium Alcaligenes bronchisepticus KU 1201. The enzyme was purified 300-fold to homogeneity, judged from the analysis of N-terminal amino acid sequence, and found to be a monomeric enzyme of apparent 24 kDa. The enzyme catalyzes a decarboxylation giving α-arylalkanoates from substituted malonates such as α-arylmalonate and α-alkyl-α-arylmalonates. The decarboxylase is not a biotin containing enzyme because avidin have no influence on the enzyme activity. In addition, the enzyme does not require known co-factors (ATP, ADP and coenzyme A) for maximum activity. The enzyme activity was inhibited by sulfhydryl agents. The electronic effect of the substituents on kcat for the enzymic decarboxylation of arylmalonates has been studied. The logarithm of relative value of kcat gave a linear correlation to Hammett's σ with a δ value of +1.9, for substituted phenylmalonates. Comparing the relative activities, it is clear that the enzyme prefers α-arylmalonates to α-aryl-α-methylmalonates. Thus, the enzyme was tentatively named as arylmalonate decarboxylase.