Abstract
Several aromatic amino compounds, which can be classified according to their aromatic nuclei into the three series, benzene, quinoline and naphthalene derivatives, have been examined as inhibitors of the α-chvmotrypsin [EC 3. 4. 4. 5]-catalyzed hydrolysis of N-acetyl-L-tyrosine ethyl ester at pH 8.0. All of the compounds were found to have the ability to interact with the enzyme in a competitive manner, aminonaphthalene derivatives being the most effective and aminobenzene derivatives being the worst inhibitors of the three series.
p-Aniino-N-acetyl-L-phenylalanine methyl ester was shown to be a good substrate of α-chymotrypsin (Km=3.3×10-3M, keat=201 sec-1 at pH 8.0), one of whose merits is its relatively high solubility. It is approximately 25 times more soluble than N-acetyl-L-tyrosine ethyl ester in pH 8.0 aqueous buffer solution.
Kinetic constants for p-nitrophenylalanine ester derivatives were also evaluated, and it was shown that while their Km values do not differ from the Km value for N-acetyl-L-tyrosine ethyl ester, their catalytic rate constants are strikingly lower than those of esters of N-acetyl-L-tyrosine, p-amino-N-acetyl-L-phenylalanine and N-acetyl-L-phenylalanine.
