Isolation of (copper, zinc)-thioneins from the livers of copper-injected rats

An enzyme capable of hydrolyzing the substrate L-alanine p-nitroanilide has been found in 18 gram-negative Enterobacteriaceae and Pseudomonas that we tested. This enzyme might be located near the cell surface. Contrastingly we have not detected this activity on colonies of the 8 gram-positive Bacillus that we tested, which suggest a taxonomic value for this test. The aminoendopeptidases found in the various gram-negative bacteria showed similar electrophoretic mobilities and immunological cross-reactivity when tested again Escherichia coli anti-aminoendopeptidase antiserum. The regulation of aminoendopeptidase biosynthesis by the endogenous level of inorganic phosphate that we previously demonstrated in E. coli has been found to exist in all gram-negative organisms tested.