The effects of phosphates, arsenates and nucleotides on l-amino acid decarboxylases

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Abstract
Addition of cetyltrimethylammonium bromide to whole cells of Escherichia coli greatly increased the rate of amino acid decarboxylation. The detergent has no effect on extracts. The effect in whole cells is taken to be due to increased permeability. Inorganic phosphate, arsenate and organic phosphates, especially adenosine phosphates, increased the rate of several bacterial amino acid decarboxylases when the pH was near the neutral point, but not at the optimum pH of the enzymes (pH 4-5). The increases in decarboxylation rate were proportional, within the range tested, to the amounts of phosphate, arsenate, or adenosine 5[image]-phosphate (AMP-5[image]) added. Two moles of phosphate or arsenate, or 1 mole of AMP-5[image], caused the decarboxylation of up to 1 extra mole of amino acid. The maximum increases were obtained with aged enzyme preparations. In contrast to the increases in rate obtained with AMP-5[image], pyridoxal phosphate stimulated only at the optimum pH of the bacterial enzymes, and had little or no effect near the neutral point. The relative activating powers of the adenosine mono-phosphates during the early stages of arginine decarboxylations were: adenosine 2[image]-phosphate > AMP-5[image]> adenosine 3[image]-phosphate, adenosine 2[image] phosphate being about twice as effective as adenosine 3[image]-phosphate. The total CO2 liberated, however, was about the same. All 3 nucleotides were unchanged. Adenosine diphosphate, inosine 5[image]-mono- and tri-phosphates, flavin mononucleotide, ribose 5-phosphate, and some other organic phosphates, expecially tetraethyl pyrophosphate increased the rate of arginine decarboxylation. Similar effects were obtained with 4 organic arsenicals: cacodylate, phenylarsonic, o-aminophenylarsonic and arsonoacetic acids. Guanylic, uridylic and cytidylic acids were among many compounds having little or no effect. Plant tissue L-glutamic acid decarboxylases (cucurbita, Daucus carota) behave like the bacteral enzymes with regard to their stimulation by phosphate, arsenate, nucleotides and pyridoxal phosphate. Under similar conditions the activity of animal tissue decarboxylases (L-glutamic, cysteine, 3:4-dihydroxy-L-phenylalanine) were not increased by adenine nucleotides, other phosphates or.arsenates.