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This paper describes the metabolism, transport and growth inhibition effects of 2-aminoethylarsonic acid (AEA) and 3-aminopropylarsonic acid (APrA). The former compound supported growth of Pseudomonas aeruginosa, as sole nitrogen source. The two arsonates inhibited the growth of this bacterium when 2-aminoethylphosphonic acid (AEP) but not alanine or NH4CI, was supplied as the only other nitrogen source. The analogy between AEA and the natural compound AEP led us to examine the in uitro and in uiuo interaction of AEA with the enzymes of AEP metabolism. The uptake system for AEP (K, 6 PM) was found to be competitively inhibited by AEA and APrA (Ki 18 pM for each). AEP-aminotransferase was found to act on AEA with a K,,, of 4 mM (3.85 mM for AEP). Alanine and 2-arsonoacetaldehyde were generated concomitantly, in a stoichiometric reaction. In viuo, AEA was catabolized by the AEP-aminotransferase since it was able to first induce this enzyme, then to be an efficient substrate. The lower growth observed may have been due to the slowness with which the permease and the aminotransferase were induced, and hence to a poor supply of alanine by transamination.

The fl form of aminomethylphosphonic acid (H+N-CH2-POaH -) crystallizes in the orthorhombic system (space group Pbca, a = 9.01 +_ 0-01, b = 9.19 _+ 0.01, c = 10.03 ___ 0.01 A; Z= 8). The crystal structure has been solved by means of Patterson techniques and refined by difference Fourier syntheses and a threedimensional least-squares procedure. The R value is 0.05 for 900 independent reflexions. Bond lengths and angles are compared with those of 2-aminoethylphosphonic acid (fl form of ciliatine) and glycine.

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