TABLE 2.
Substrate specificity of ApeEa
| Type | Substrates |
|---|---|
| Hydrolyzed | β-Naphthyl esters of N-acetyl, N-benzoyl, and N-benzyloxycarbonyl Phe and of caproic acid; α- and β-naphthyl esters of acetic, propionic, and butyric acids; p-nitrophenyl esters of all straight-chain fatty acids C6 to C16 |
| Not hydrolyzed | β-Naphthyl esters of N-acetyl Leu, N-methyl-N-toluene-p-sulfonyl Lys, and N-acetyl Arg and of lauric and palmitic acids; naphthol AS esters of propionic, phenylpropionic, and benzoic acids; p-nitrophenyl esters of N-acetyl Phe; β-naphthylamides of N-benzoyl Phe, Leu, Trp, and Leu-Phe; p-nitroanilide of N-acetyl Phe; peptidesb PheAsp, AspPhe, PheGly, Phe4, Phe5, and PheGlyGly |
a
Based on qualitative assays using Triton X-100 membrane extracts as described in Materials and Methods. Membranes from a wild-type strain, an ApeR− strain overproducing ApeE, and an ApeE− strain were compared. In all cases in which hydrolysis was observed, the overproducer strain showed the most rapid color development and the ApeE− strain showed no activity. The most rapidly hydrolyzed compounds were the α- and β-naphthyl esters of butyric and caproic acids. Naphthol AS, 3-hydroxy-2-naphthoic acid anilide.
b
Peptide hydrolysis was tested after electrophoresis of detergent extracts on nondenaturing polyacrylamide gels.