Neisseria catarrhalis produces arylamidase intracellularly and is one of the gram-negative bacteria producing exceptionally large amounts of this enzyme.In general, gram-positive bacteria do not produce this enzyme. Arylamidase from N. catarrhalis was purified by salt fractionation, chromatography, and density gradient ultracentrifugation. Its sedimentation coefficient was 6.6; l-alanine-β-naphthylamide (βNA) was the most rapidly hydrolyzed amino acid-βNA. The enzyme had pKe values of 6.1 and 8.7 and pKes values of 7.1 and 7.9; only those amino acid-βNA compounds of the l configuration were susceptible to hydrolysis. Arylamidase catalyzed stepwise hydrolysis of dipeptide-βNA, beginning with the N-terminal residue. Substrates having amino acid residues with larger R groups, such as leucine, interacted much more effectively with enzyme. The significance of the predominate occurrence of arylamidase activity in gram-negative bacteria and the role of this enzyme in the physiology of these organisms remain unclear. It has been established, however, that arylamidase is distinct from leucine aminopeptidase
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