Regulatory Properties of an Inducible Aliphatic Amidase in a Thermophilic Bacillus

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Abstract
A thermophilic bacillus growing on acetamide as C and N sources produces an inducible amidase. This amidase hydrolyzed the following amides in decreasing order of activity, in comparison with acetamide (1.00): propionamide (0.97), fluoroacetamide (0.84), formamide (0.35) and glycinamide (0.12). Cyanoacetamide, dimethylacetamide, dimethylformamide and urea also induced the synthesis of the amidase, but were not substrates of the enzyme. Studies with protoplasts suggest that the amidase is located in the cytoplasm. Glucose strongly inhibited amidase synthesis; limiting N did not release this inhibition. Urea strongly inhibited amidase activity in a competitive manner; the inhibition caused by iodoacetamide and cyanoacetamide was non-competitive. Thioacetamide and thiourea were effective inhibitors of enzyme induction. Bacteria grown on a succinate-minimal medium exhibited a lag in amidase synthesis, which was eliminated by decreasing the concentration of succinate. Acetate- or pyruvate-grown cultures behaved similarly, while those grown on alanine or glutamate exhibited no lag in enzyme induction. In the mutant strain E21, repression of amidase synthesis by glucose was much less evident, and no lag for induction was apparent with any of the other C sources mentioned.

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